NBS MONOGRAPH 87

Oxidation of

Polycyclic, Aromatic Hydrocarbons

A Review of the Literature

U.S. DEPARTMENT OF COIMIMERCE

NATIONAL BUREAU OF STANDARDS
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UNITED STATES DEPARTMENT OF COMMERCE • John T. Connor, Secretary

NATIONAL BUREAU OF STANDARDS • A. V. Astin, Director

Oxidation of Polycyclic, Aromatic

Hydrocarbons

A Review of the Literature

R. Stuart Tipson

Institute of Materials Research

National Bureau of Standards

Washington, D. C.

National Bureau of Standards Monograph 87

Issued September 17, 1965

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 Price 40 cents
Library of Congress Catalog Card Number: 65-60062
Contents

Page

. Introduction 1

. Oxidants for polycyclic, aromatic hydrocarbons 3

. Kinds of oxidation of polycyclic, aromatic hydrocarbons 3

3.1. Classes of products 3

3.2. Positions of attack 3

. Reactive centers 11

4.1. The most reactive center 11

4.2. para Reactive centers __ 14

4.3. ortho Reactive centers 14

4.4. Eifect of conformation of the hydrocarbon 19

4.5. Effect of methyl substituents 20

5. One-center attack 20

5.1. Oxidation resulting in substitution 20

5.1.1. Oxidative coupling 21

6. Two-center attack 21

6.1. Addition to two reactive centers 21

6.1.1. para Addition 21

6.1.2. ortho Addition 22

6.2. Oxidation to the dione 22

7. Pre-oxidative behavior 24

7.1. With oxygen 24

7.2. With strong acids 24

7.3. With ultraviolet light (non-oxidative dimerization) 25

8. Agents causing one-center attack 26

8.1. At an active methylene group 26

8.1.1. Chromium trioxide 26

8.1.2. Lead tetraacetate 27

8.1.3. Oxygen 27

8.1.4. Oxygen and ultraviolet light 27

8.1.5. Ozone 27

8.1.6. Selenium dioxide 27

8.2. Oxidation of one reactive methylidyne (methine) grouping —- 28

8.2.1. Benzoyl peroxide 28

(a) Substitution 28

(b) Oxidative coupling 28

8.2.2. Hydrogen peroxide catalyzed by osmium tetroxide 29

8.2.3. Lead tetraacetate 29

8.2.4. Oxygen and ultraviolet light 30

8.2.5 Peroxybenzoic acid 30

9. Agents causing two-center attack 30

9.1. At two, nonadjacent, methylidyne (methine) groupings 30

9.1.1. Benzoyl peroxide 30

9.1.2. Chromium trioxide 30

9.1.3. Hydrogen peroxide catalyzed by osmium tetroxide 30

9.1.4. Lead tetraacetate 31

9.1.5. Nitric acid 31

9.1.6. Nitric oxide and ultraviolet light — 33

9.1.7. Nitrogen dioxide (addition) 33

9.1.8. Organic peroxy acids 33

9.1.9. Oxygen 33

9.1.10. Oxygen and ultraviolet light (transannular addition) 34

9.1.11. Oxygen and ultraviolet light, with catalysts 35

9.1.12. Oxygen with various catalysts 36

9.1.13. Ozone 37

9.1.14. Selenium dioxide 39

9.1.15. Miscellaneous reagents 39
9.2. At a "double" bond 39

9.2.1. Addition to a "double" bond 39

1. Hydrogen peroxide, catalyzed by osmium tetroxide 39

2. Osmium tetroxide-pyridine _ 40

3. Oxygen _ 42

4. Peroxybenzoic acid 42

9.2.2. Addition to, and rupture of, a "double" bond _ 42

1. Chromium trioxide 42

2. Nitric acid 42

3. Organic peroxy acids _ 43

4. Oxygen, catalyzed by vanadium pentoxide 43

5. Ozone 43

(a) In a nonparticipating solvent 43

(b) In a participating solvent _ 45

6. Potassium permanganate _ 46

9.2.3. Oxidation of ort/io-methine groupings 46

1. Chromium trioxide 46

2. Hydrogen peroxide, catalyzed by osmium tetroxide 46

3. Iodic acid _ 47

4. Osmium tetroxide and sodium periodate 47

5. Peroxyacetic acid 47

6. Potassium permanganate 47

7. Ruthenium dioxide and sodium periodate 48

8. Selenium dioxide —. 48

10. Oxidative degradation of an alkyl side-chain 48

10.1. Chromium trioxide 48

10.2 Nitric acid _ _ 48

10.3 Potassium permanganate _ 49

11. Summary of action of various oxidants _ 49

12. References 49

IV
Oxidation of Polycyclic, Aromatic Hydrocarbons^

A Review of the Literature

R. Stuart Tipson

A survey has been made of the literature on the oxidation of polycyclic, aromatic

hydrocarbons. Information has been assembled on (1) the oxidants effective in the oxidation of such hydrocarbons, (2) the relative reactivity of the hydrocarbons, (3) the conditions under which oxidation proceeds, (4) the chemical mechanisms involved

when such oxidations occur, and (5) the products formed.

1. Introduction

Pyrolysis or incomplete combustion of carbon-containing materials at high temperatures gives rise to polycyclic, aromatic compounds. Consequently, many compounds of this

nature have been detected as pollutants in the air of large cities, particularly where dispersal is retarded.

Such air pollutants include many polycyclic, aromatic hydrocarbons and certain of

their oxidation products. The majority of the hydrocarbons of this kind that have thus

far been found in polluted air are listed in table 1, in the order of increasing size of the

molecule, together with the corresponding Ring Index number (RRI No.) [1].- Some of

these hydrocarbons are carcinogenic to animals (see table 1) and, possibly, to man. Eleven

carcinogenic hydrocarbons have thus far been detected in automobile exhaust fumes ; five are also present in practically all airborne particles (such as dust and soot) [2].

From particulate matter, obtained from polluted air, quinones of such hydrocarbons

as pyrene (5262),^ benzo[a]pyrene (6399), and dibenzo[c?e'/,/);/io]chrysene (7033), as well

as other oxidized organic compounds (largely unidentified as yet), have been isolated and

identified [3].

This suggests that, after release of reactive hydrocarbons into the atmosphere, some

oxidation may normally occur in the air. Indeed, thirty years ago, it was discovered [4]

that, on exposure to air containing ozone, the carcinogenic benzo [a] pyrene (6399) is transformed into less carcinogenic or noncarcinogenic material. Such oxidation is to be

expected, as polluted air contains a number of oxidants : the nitrogen oxides, oxygen, and

ozone of unpolluted air, together with such compounds as sulfur dioxide, produced by

combustion.

The oxidation of polycyclic, aromatic hydrocarbons is also of interest because, in

evolving ways for reducing air pollution, attention is currently being given to the development of chemical devices for oxidizing atmospheric pollutants produced by incomplete

combustion and pyrolysis in automobile and Diesel exhaust fumes.

1 This Monograph was prepared as part of a study of the oxidation of polycyclic, aromatic hydrocarbons being conducted in the Organic Chemistry Section under the direction of Horace S. Isbell and the author. The work was partly supported by the

Division of Air Pollution, Public Health Ser\-ice, U.S. Department of Health. Education, and Welfare.

- Figures in brackets indicate the literature references at the end of this Monograph. The references for tables are given at

the end of the respective tables.

3 The number in parentheses, following the name of a hydrocarbon, is the RRI No. for that hydrocarbon, as given in [1]. This number is definitive; it is used because of the multiplicity of names often found in the literature for the same hydrocarbon,

but may be omitted when the structure is depicted.

1
Table 1. Some polycyclic, aromatic hydrocarbons found

in polluted air, automobile exhaust, and Diesel exhaust

RRI No Tif Vfl rof r hnn ZvtJi CI ClU^CO

1754 Ns-phthalGnc A I 1754 b 2-methvl- A

3127 Fluorenc A 1 2 3133 Acenaphthylene A I 3133i> Acenaphthene A I 3618 AnthracGriG A ] 2 3619 Phorifinthrene A 1 2 4773 1 1 i/-Benzo[6]fluorenp A 2 4778 1 1 /f-Benzo[ct]fluorene A 2 4780 7//^- Benzo[r] fluorenc A 2 4799 Pluoranthenc A I 5253 13enz[ct]anthrac6ne ® A,B,C 1 3 5254 Chrysene

a,'b'c 1 3 4 5262 Pyrene a^c'd 1 4 5262 1-niethy I- 'a' 5262 2 7-dirnpthyl- A X 6070 B6nz[6]tioephenanthr\'lenG A,C,D 3,5,6

6075 BenzofA'jfluoranthene A ' C ' D 5,6

6078 Benzo[j]fluoranthene 'c

3 6092 B6'nzo[^/? z ]fluoranthen6 A 5 6383 Dibenz[a , /?]anthracene ° . c 3 6399 Benzo[(2]pvrene

A,B,C,D 1,3,4,7 6400 Benzo[e]pvrene 0 A,B,C 1,3,4

6401 Pervlcne A 1 9508 Indeno[l 2 3-rrf]pyrene

c 3 7001 Dibenzo[a,/]naphthacene A, CD 1,6 7026 Napht ho[ 1,2,3, 4-c?^'/]ch^ysene " C 3 7030 Dibenzo[^/e/, p]chrysene « C 3 7033 Dibenzo[r/e/, wnolchrysene A, CD 1,7,8 7036 Benzo[ghi]peTy\ene A,B,C,D 1-5,8 7392 Coronene A 1,2,5

"Key: A, air; B, practically all airborne, particulate samples; C, automobile exhaust; D, Diesel ex- haust.

"Derivative. "Reported to be carcinogenic to experimental animals.

References for table 1

1. E. Kennaway and A. J. Lindsey, Brit. Med. Bull. 14, 124 (1958).

2. E. Sawicki, T. R. Hauser, W. C. Elbert, F. T. Fox, and J. E. Meeker, Am. Ind. Hyg. Assoc. J. 23, 137

(1962).

3. E. Sawicki, Chemist-Analyst 53 (No. 1), 24 (1964).

4. P. Kotin, H. L. Falk, P. Mader, and M. Thomas, A.M.A. Arch. Ind. Hyg. Occ. Med. 9, 153 (1954).

5. P. Kotin and H. L. Falk, Cancer 12, 147 (Jan.-Feb. 1959).

6. T. W. Stanley, Chemist-Analyst 49, 47 (June 1960).

7. P. Kotin, H. L. Falk, and M. Thomas, A.M.A. Arch. Ind. Hyg. Occ. Med. 9, 164 (1954).

8. P. Kotin, H. L. Falk, and M. Thomas, A.M.A. Arch. Ind. Health 11, 113 (1955).

In considering the fate of these hydrocarbons and methods for minimizing their effects as air pollutants, it thus became of interest to assemble all of the available information on

(1) the oxidants effective in the oxidation of polycyclic, aromatic hydrocarbons, (2) the

relative reactivity of the hydrocarbons, (3) the conditions under w^hich oxidation proceeds,

(4) the chemical mechanisms involved vi^hen such oxidations occur, and (5) the products

formed. The present Monograph is a review of the oxidation of selected representatives of

the group of polycyclic, aromatic hydrocarbons by oxidant systems containing oxygen. All

of the principal methods which have been investigated will be discussed, but the treatment

is not intended to be exhaustive. Biological oxidation will not be considered.

2
2. Oxidants for Polycyclic, Aromatic Hydrocarbons

The action of many different oxidants on a variety of polycyclic, aromatic hydrocarbons has been rather perfunctorily studied during the past hundred years, and the results are widely scattered through the literature. In only a few instances have systematic in- vestigations been undertaken.

Listed alphabetically in tables 2 and 3 are those oxidants whose action on such hydrocarbons has been the most systematically examined ; the effect of each of these six oxidants on eight different hydrocarbons is summarized in table 3. Oxidants that have received less attention in this field are listed alphabetically in table 4. For only one oxidant studied to date, namely osmium tetroxide-pyridine, has the

action of the oxidant (both as regards positions of attack and kind of product) been found

to be invariant (see table 3), regardless of the structure of the hydrocarbon oxidized. In

all other instances, the kind of oxidation effected by any one oxidant depends on the character of the hydrocarbon being oxidized. Furthermore, for some oxidants, the oxidizing

action of the oxidant depends on the conditions under which the oxidation is performed.

Consequently, references are provided in tables 2 and 4 to the sections of this article

wherein the particular oxidizing action is described.

Table 2. Principal oxidants for polyr.yclic, aromatic hydrocarbons

Oxidant Action described in sections

1 Benzovl peroxide 8.2.1; 9.1.1

2 Chromium trioxide (or sodium dichromate) 8.1.1; 9.1.2; 9.2.2.(1); 9.2.3.(1); 10.1

3 Hvdrogen peroxide plus osmium tetroxide 8.2.2; 9.1.3; 9.2.1.(1); 9.2.3.(2) 4 Osmium tetroxide plus pyridine (and hydrolysis) 9.2.1. (2) 5 Ozone (with subsequent treatment) 8.1.5; 9.1.13; 9.2.2.(5)

6 Peroxyacetic acid 9.1.8; 9.2.2.(3); 9.2.3.(5)

3. Kinds of Oxidation of Polycyclic, Aromatic Hydrocarbons

As may be seen from table 3, the kind of oxidation caused by an oxidant acting on any one hydrocarbon embraces two features : (a) the class of product, and (b) the positions of attack.

3.1. Glasses of Products

The various kinds of oxidation product are discussed in detail in sections 8 to 10. As

may be seen from table 3, those often encountered include acyloxy derivatives, diols, or o- or p-diones. Other possible products are epoxides, hydroperoxides, and peroxides. If a bond is ruptured, the product may be a dialdehyde, an aldehydic acid, or a dicarboxylic acid.

3.2. Positions of Attack

In some instances, one-center attack (resulting in substitution) may occur, as in the

oxidation of benzo [a] pyrene with benzoyl peroxide (see table 3) to give a benzoyloxy

derivative. A similar effect is caused by lead tetraacetate (see pp. 27 and 29), although

two-center addition followed by elimination may be involved. One-center attack is also

encountered in hydrogen abstraction at a reactive center by an oxidant, to give a free

radical, followed, for example, by combination of two such radicals to afford a dimer.

8
Table 3. Products from the oxidation of some polycyclic, aromatic hydrocarbons

RRI Oxidants

No. Hydrocarbon (C^H3CO)202 Refer

ences CrO^ ^

References

1754

Naphthalene

V

1-ol benzoate +

2- ol benzoate +

1- phenyl'haphthalene +

2- phenylnaphthalene +

binaphthyls (1,1'-, 1,2'-, and 2,2'-)

1,2 (para) 1,4-dione

j

3

3618

etc: 10 //- Anthracene

9-ol benzoate + 14 15 (para) 9,10-dione (para) 9,10-dicne

3619

Phenanthrene

"No reaction" 14 (ortho) 9,10-dione + diphenic acid

20

References for table 3

1. A. Perret and R. Perrot, Helv. Chim. Acta 28, 558 (1945).

2. D. I. Davies, D. H. Hey, and G. H. Williams, J. Chem. Sec. 1958, 1878.

3. C. E. Groves, J. Chem. See. 26, 209 (1873). N. H. J. Miller, J. Russ, Phys. Chem. See. 16, 414 (1884). F. R. Japp and N. H. J. Miller, J. Chem. See. 39, 220 (1881). E. A. Braude and J. S. Fawcett, Org.

Syntheses 33, 50 (1953).

4. N. A. Milas, U. S. Pat. 2,395,638 (1946).

5. J. W. Cook and R. Schoental, J. Chem. See. 1950, 47.

6. J. W. Cook and R. Schoental, J. Chem. Soc. 1948, 170; Nature 161, 237 (1948).

4
and oxidation products

H202-OsO^ References

OsO, —C^H^N

4 5 5 References

O3 References CH^CO-OOH References

l-ol + 4,5 Reacts 6 7 (^) 1,4-dione 8-13

(£) 1,4-dione +

(o) + 1,2-dione

+a::

(0) attacks

C1-C2 - a:: +

+a:: az

(£) 9^10-dione

(o) 1,2,3,4-

tetra-hydroly2,3,4-

tetrol

6 (£) attacks

C-9 and

C-10

9,10-

dione (62%)

(0) attacks

C1-C2

16-18

(£) 9,10-dionq

8,

9,

U,

19a

9-oL +

(o) 9,10-dihydro9,10-diol + 9,10-dione

5

(o) 9,10-

dihydro9,10-diol

21 (£) attacks

C9-C10

O^C OHO

17,18,

22,23

(0) 9,10-dione +

diphenic acid

8,

9,

11,

24

+ diphenic acid +

+ diphenic acid

7. C. Harris and V. Weiss, Ann. 343, 369 (1905). L.Seekles, Chem. Weekblad 20, 261 (1923); Rec. Trav. Chim. 42, 706 (1923). L. W. F. Kampschmidt and J. P. Wibaut, Rec. Trav. Chim. 73, 431 (1954).

P. S. Bailey and F. J. Garcia-Sharp, J. Org. Chem. 22, 1008 (1957). P. S. Bailey, S. S. Bath, F. Dobinson, F. J. Garcia-Sharp, and C. D. Johnson, J. Org. Chem. 29, 697 (1964). C. D. Johnson and P. S. Bailey, J. Org. Chem. 29, 703 (1964).

8. G. G. Henderson and R. Boyd, J. Chem. Soc. 97, 1659 (1910).

9. G. Charrier and A. Moggi, Gazz. Chim. Ital. 57, 736 (1927).

10. J. Boeseken and G. Slooff, Rec. Trav. Chim. 49, 100 (1930).

11. R. T. Arnold and R. Larson, J. Org. Chem. 5, 250 (1940).

12. E. Ibuki, J. Chem. Soc. Japan, Pure Chem. Sect. 70, 286 (1949).

13. Y. Odaira, S. Takigawa, and S. Tsutsumi, Kogyo Kagaku Zasshi 62, 89 (1959).

14. I. M. Roitt and W. A. Waters, J. Chem. Soc. 1952, 2695.

5
Table 3. Products from the oxidation of some polycyclic, aromatic hydrocarbons—Cont.

RRI Oxidants

No, Hydrocarbon (C^H5CO)202 References CrO^ References

5253

Benz[ a] anthracene

7-ol benzoate 14 (£) 7yl2-dione 25

5254

Chrysene

"No reaction" 14 (£) 5^6-dione 28

5262

^^^^^^

Pyrene

1^6-dione '.1/3) + l;8-dione (2/3)

j9,30

15. J. Fritzsche, J. Prakt. Chem. [1] 106, 274 (1869). C. Graebe and C. Liebermann, Ann. (Suppl.) 7, 257 (1870). W. H. Beisler and L. W. Jones, J. Am. Chem. Soc. 44, 2296 (1922).

16. Heinemann, British Pat. 5514 (1915). I. M. Roitt and W. A. Waters, J. Chem. Soc. 1949, 3060. P. S. Bailey and J. B. Ashton, J. Org. Chem. 22, 98 (1957). P. S. Bailey, Chem. Ind. (London) 1957, 1148. P. G. Copeland, R. E. Dean, and D. McNeil, J. Chem. Soc. 1961, 3858. F. Dobinson and P. S. Bailey, Chem. Ind. (London) 1961, 632.

17. P. G. Copeland, R. E. Dean, and D. McNeil, Chem. Ind. (London), 1959, 329.

18. P. G. Copeland, R. E. Dean, and D. McNeil, Chem. Ind. (London), 1960, 98.

19. G. Charrier and G. B. Crippa, Gazz. Chim. Ital. 57, 741 (1927).

19a. A. R. Leeds, Ber. 14, 1382 (1881).

6
and oxidation products

H^O^—OsO^ ReferencesOsO, -C3H3N Refer- ences

Refer- ences CH^CO-OOH References

(£) 7^12-dione

(20%)

(o) + 5,6-

dlhydro5,6-diol + 5^6-dione

(15%)

6,26

(o) 5,6-

dihydro5,6-diol

(£) attacks

C5-C6

17,

18,

22, 27

(£) 7,12-dione +

11, 22

I

(£) 5,6-dione (o) 5,6-

dihydro5 , 6-diol

(o) attack?

C5-C6

17, 22

(o) 22

-\-

(in tert-BuOH)

1,6-dione +

(o) (in Me2C0)

4,5-dione

18,

30,

32

11 1,6-dione +

1,8-dione

31 dihydro4,5-diol

20. R. Fittig and E. Ostermayer, Ann. 166, 361 (1873). C. Graebe, Ann. 167, 131 (1873). R. Anschuetz

and G. Schultz, Ann. 196, 32 (1879). L. Oyster and H. Adkins, J. Am. Chem. Soc. 43, 208 (1921).

F. Bischoff and H. Adkins, J. Am. Chem. Soc. 45, 1030 (1923). H. W. Underwood, Jr., and E. L. Kochmann, J. Am. Chem. Soc. 46, 2069 (1924). F. J. Moore and E. H. Huntress, J. Am. Chem. Soc.

49, 1324 (1927).

21. R. Criegee, B. Marchand, and H. Wannowius, Ann. 550, 99 (1942).

22. P. G. Copeland, R. E. Dean, and D. McNeil, J. Chem. Soc. 1961, 1232.

23. W. J. Schmitt, E. J. Moriconi, and W. F. O'Connor, J. Am. Chem. Soc. 77, 5640 (1955). J. P. Wibaut

and T. J. de Boer, Koninkl. Ned. Akad. Wet. Proc. B59, 421 (1956). P. S. Bailey, J. Am. Chem, Soc.

78, 3811 (1956). P. S. Bailey and S. B. Manthia. J. Org. Chem. 21, 1335 (1956); 23, 1089 (1958).

W. F. O'Connor, W. J. Schmitt, and E. J. Moriconi, Ind. Eng. Chem. 49, 1701 (1957). J. P. Wibaut

and T. J. de Boer, Rec. Trav. Chim. 78, 183 (1959). M. G. Sturrock, E. L. Cline, and K. R. Robinson, J. Org. Chem. 28, 2340 (1963). R. H. Callighan and J. 0. Hawthorne, U. S. Pat. 3,118,934

(1964).

7
Table 3. Products from the oxidation of some polycyclic, aromatic hydrocarbons—Cont.

RRI

No. Hydrocarbon

Oxidants

(C^H3CO)202 References CrO^ References

6383

Dibenz[a,hlanthracene

(1) Oxygen present

(£) 7,14-dione

(2) Oxygen absent

no reaction

14 (_£) 7,14-dione

(major)

+

(o) 5^6-dione

(minor)

33

6399 6-ol benzoate 14 1^6-dicne + 30,36

3^6-dicne

11

h 5

1

Benzo [a] pyrene

24. W. F. O'Connor and E. J. Moriconi, J. Am. Chem. Soc. 73, 4044 (1951); Ind. Eng. Chem. 45, 277

(1953). W. F. O'Connor, F. T. Wallenberger, and E. J. Moriconi, Brennstoff-Chem. 38, 170 (1957).

S. Havel and J. A. Weigner, Chem. Prumysl 10, 10 (1960). Ruetgerswerke A.-G., Brit. Pat. 853,369

(1960).

25. C. Graebe, Ann. 340, 249 (1905). K. Dziewonski and E. Ritt, Bull. Intern. Acad. Polonaise, 1927A,

181.

26. G. M. Badger, J. Chem. Soc. 1949, 456.

27. E. J. Moriconi, W. F. O'Connor, and F. T. Wallenberger, Chem. Ind. (London) 1959, 22; J. Am. Chem.

Soc. 81, 6466 (1959).

28. C. Liebermann, Ann. 158, 299 (1871). E. Bamberger and C. Burgdorf, Ber. 23, 2433 (1890). C. Graebe

and F. Hoenigsberger, Ann. 311, 257 (1900).

29. C. Graebe, Ann. 158, 285 (1871). G. Goldschmiedt, Monatsh, 4, 309 (1883). E. Bamberger and M.

Philip, Ann. 240, 147 (1887).

30. H. Vollmann, H. Becker, M. Corell, and H. Streeck, Ann. 531, 1 (1937).

8
and oxidation products

H202-OsO^ References

OsO, —C^H^N

4 5 5 Refer- ences O3 References CH^CO-OOH References

(g) 7,14-diene +

(o) 5,6-dione +

(35%)

5

(o) 5,6,12,

13-tetrahrycko5,6,12,13-

tetrol

6 (0) attacks

C5-C6

and C12-C13 ^^^^

+

34

(£) 7,14-dione +

(0) 5,6-dione +

(60-80%)

35

1,6-dione +

3,6-dione +

(o) 4,5-dione

5

(0) 4,5-

dihydro4,5-diol

6

1,6-dione OJi) + 3,6-dione

(25%)

(0) + 4,5-

dione

(trace)

37

31. F. G. Oberender and J. A. Dixon, J. Org. Chem. 24, 1226 (1959).

32. L. F. Fieser and F. C. Novello, J. Am. Chem. Soc. 62, 1855 (1940). M. S. Newman and H. S. Whitehouse, J. Am. Chem. Soc. 71, 3664 (1949). G. M. Badger, J. E. Campbell, J. W. Cook, R. A. Raphael,

and A. I. Scott, J. Chem. Soc. 1950, 2326. C. Danheux, L. Hanoteau, R. H. Martin, and G. Van Binst,

Bull. Soc. Chim. Beige 72, 289 (1963).

33. R. Weitzenboeck and A. Klingler, Monatsh. 39, 315 (1918). E. Clar, Ber. 62, 350 (1929). J. W. Cook,

J. Chem. Soc. 1933, 1592.

34. E. J. Morlconi, G. W. Cogswell, W. J. Schmitt, and W. F. O'Connor, Chem. Ind. (London) 1958, 1591. E. J. Moriconi, W. F. O'Connor, W. J. Schmitt, G. W. Cogswell, and B. P. Fuerer, J. Am. Chem. Soc.

82, 3441 (1960).

35. B. L. Van Duuren, I. Bekersky, and M. Lefar, J. Org. Chem. 29, 686 (1964).

36. J. W. Cook, R. S. Ludwiczak, and R. Schoental, J. Chem. Soc. 1950, 1112.

37. E. J. Moriconi, B. Rakoczy, and W. F. O'Connor, J. Am. Chem. Soc. 83, 4618 (1961).

9
Table 4. Some oxidants for polycyclic, aromatic hydrocarbons

Oxidant Action described in sections

Lead tetraacetate .• 8.1.2; 8.2.3; 9.1.4

Nitric acid, nitrates, nitrites 9.1.5; 9.2.2.(2); 10.2

Nitrogen oxides 9.1.6; 9.1.7 Osmium tetroxide plus sodium periodate 9.2.3.(4)

Oxygen 8.1.3; 9.1.9; 9.2.1.(3)

Oxygen plus ultraviolet light 8.1.4; 8.2.4; 9.1.10; 9.1.11 Oxygen plus vanadium pentoxide 9.1.12; 9.2,2.(4)

Oxygen plus various catalysts 9.1.12 Potassium permanganate 9.2.2. (6); 9.2.3. (6); 10.3 Ruthenium dioxide plus sodium periodate 9.2.3.(7) 8.1.6; 9.1.14; 9.2.3.(8) Miscellaneous oxidants 8.2.5: 9. 1 . 15; 9.2.1.(4); 9.2.3.(3)

On the other hand, many oxidants effect two-center attack, either stepwise or simultaneous. For some polycyclic, aromatic hydrocarbons (for example, phenanthrene and

chrysene), the posih'ows of attack are invariant (see table 3), regardless of the oxidant

Phenanthrene (3619) Chrysene (5254)

employed. However, the kind of product depends on the oxidant employed. Thus, whereas

osmium tetroxide-pyridine causes hydroxylation of phenanthrene to the 9,10-diol, ozone

ruptures the bond at C9-C10, and chromium trioxide gives the 9,10-dione (together with some diphenic acid formed by rupture of the bond at C9-C10).

In other instances, the positions of attack on the same hydrocarbon are different for

different oxidants. Thus, whereas osmium tetroxide-pyridine attacks the ortho positions

at C1-C2 and C3-C4 of anthracene [5], chromium trioxide attacks the para positions at

ortho Attack

, ^

(I)OsO^-C3H3N

' 2

3^

(2) hydrolysis

Anthracene (3618)

C-9 and C-10 of this hydrocarbon [6],

para Attack 4^

do

10

t

1, 2, 3, 4 - Tetrahydrol, 2, 3, 4-anthratetrol

0

II CrO,

Anthraquinone

10
Again, in some instances, a single oxidant acting on a single hydrocarbon may simultaneously attack different molecules of that hydrocarbon either ortho or para. For example, chromic acid oxidizes dibenz [a,/i.] anthracene to a mixture containing (mainly) the

p-dione with some o-dione.

Dibenz[a^h] anthracene (6383) 7,14-Dione 5,6-Dione

(major) (minor)

The two kinds of oxidation mentioned for anthracene are prototypes of the positions

of attack generally encountered in two-center attack on polycyclic, aromatic hydrocarbons,

namely, ortho and para. In the former (ortho attack), reaction occurs at a reactive bond,

and leads either to formation of the o-diol or o-dione or to rupture of this bond. The lat- ter (para attack) is exemplified by transannular addition and by the formation of p-diones.

It is probable that oxidation to a p-dione actually involves two separate one-center attacks,

the first occurring at the reactive center having the lowest localization energy. This stepwise attack may account also for the fact that such hydrocarbons as pyrene (5262) and

benzo[a]pyrene (6399), which have no reactive para centers, undergo "pseudo-para"

attack.

Finally, if the hydrocarbon has an alkyl side-chain, the side chain may undergo oxidative degradation ; and if the hydrocarbon has one or more reactive methylene groups in one or more of the rings, these may be the sites of attack.

4. Reactive Centers

For benzene, all of the carbon atoms are equally reactive; but, in the polycyclic,

aromatic hydrocarbons, some carbon atoms may be more reactive than others. Thus,

experience has shown that, in naphthalene, C-1 is more reactive than C-2, and that, in

10

Naphthalene (1754) Anthracene (3618)

anthracene, C-9 (= C-10) is much more reactive than the other carbon atoms present.

Mathematical evaluations of the reactive centers of conjugated hydrocarbons, made

by the valence-bond method and by the molecular-orbital method, have been summarized

by the Pullmans [7] . In the following brief discussion, some predictions obtained by the

molecular-orbital method are indicated.

4.1. The Most Reactive Center

For an electrophilic or nucleophilic attack, or a radical substitution, to proceed at a

given carbon atom of a conjugated hydrocarbon, the electronic structure of the hydrocarbon has to be disturbed in such a way that the appropriate number of electrons become

localized at the carbon atom attacked. The amount of energy needed for producing this

11
Table 5. Localization energies of the various centers

of some polycyclic, aromatic hydrocarbons'

Carbon atom number''

10 11 12 13

1.81 1.57 1.42

1.32

1.98

1.93 1.68 2.00

1.95 1.97 1.86 1.80

1.86

1.92 2.02

1.51 1.38

1.68

1-44

1.89

1.69

1.54

.96

.89

.92

.08 .99

.97

18

16 .85

.01 2.12

2.31 2.27 2.25

2.12

2.13 2.07

1.99 2.08

2.13

2.16

2.04 2.02

2.10

2.17

1 51

1.41 1.63 1.33

1.81

1.26. 1 26

1.84 1.80

1.64 2.00

1.85

1.83

1.96 1.90 1.83

1.81 2 02

1.68

1.55 1.73

1.13 0.89

1.66

1.53 1.36

1.71 1.66

1.79

1.67

1.68

1.55

1.13 0.80

1.66

1.58

1.58

1.35

1.13 1.63 1.09

1.36

1.98

1.46

1.92

1.77 1.861.75 1-44

1.48

1.50 1.70 2.00

1.70

1.71 1.441.51

1 79 1.79

1.67

1.86 1.86

1 51 1.15

1.90

1.55

1 51

2. 12 1.68

1.73 1.681.81 1.81

2.08

1 .50

1.98

0.80

1.12

1.47

1.78

Calculated, in arbitrary units, by M. J. S. Dewar, J. Am. Chem. Soc. 74, 3357 (1952). •Boldface numbers indicate the most reactive centers, and italic numbers indicate the next most re- active centers.

localization is called the localization energy of this carbon atom. Obviously, the higher its localization energy, the lower is the reactivity of the center ; the lower the localization energy, the higher the reactivity.

Dewar [8] has calculated the localization energies of the various positions in the molecule for a number of alternant hydrocarbons. The results are collected in table 5, with the

RRI numbers for the respective hydrocarbons ; the names of the hydrocarbons are omitted

from table 5, but are given in table 6. The most reactive centers, together with the next most reactive centers, are given in

table 6, from which it may be seen that, for the linear hydrocarbons, the most reactive

4-/0 s b

Naphthalene Anthracene Naphthacene Pentacene

center predicted corresponds to that in naphthalene (1=4) or anthracene (9 = 10). For

angular hydrocarbons containing an anthracene moiety in which the carbon atoms corre7 S

Benz[ a] anthracene Benzo [a] naphthacene

spending to the anthracenic C-9 and C-10 are free, these were predicted to be the reactive

centers, even though a phenanthrene moiety in which the phenanthrenic C-9 and C-10 are

free should be present.

12
Table 6. The most reactive and next most reactive centers

{predicted) for some polycyclic, aromatic hydrocarbons'

RRI

No. Hydrocarbon

Most reactive center •> Next most reactive center

1754 3618

5252

6376

5253 6377 6378

6381 6382

6383

3619

5254

5255 6384

5256 5262

6399 6400

6401

Linear Naphthalene

Anthracene

Xaphthacene

Pentacene

Angular

(a) Reactive anthracene moiety . . Benz[a]anthracene

Benzo[a]naphthacene

Pentaphene

Dibenz[a , cjanthracene

Dibenz[a,yianthracene

Dibenz[a , /ijanthracene

(b) Reactive phenanthrene moiety

Phenanthrene

Chrysene

Benzo[c]phenanthrene

Picene Condensed ring systems

Triphenylene P>Tene

Benzo[a]p\Tene

Benzo[e]pyrene

Perylene

°1*( = 4* = 5 = 8) 9*( = 10*) 5*( = 6=11 = 12* 6*( = 13*)

5*( = 8) 9*( = 14*) 7*

7*( = 14*)

°9( = °10)

«6( = 12)

'5( = 8)

'5( = 8)

°1*( = 4* = 5 = 8 = 9=12)

1( = 3 = 6 = 8) 6

3( = 6) 3( = 4 = 9 = 10)

°2( = 3 = 6 = 7) oi(=4 = 5 = 8)

ci( = 4 = 7=io)

5( = 7 = 12 = 14)

12*

13*

13( = 14*) n0( = 13) 14*

•5( = 12)

'1(=8)

'1( = 7) '4(=9)

13( = 14)

°2( = 3 = 6 = 7 = 10=11)

°4( = °5 = 9 = 10)

11( = 8)

1( = 6 = 7 = 12)

•From M. J. S. Dewar, J. Am. Chem. Soc. 74, 3357 (1952).

"The asterisks indicate a para pair, and the ° superscripts indicate an ortho pair of reactive centers. "The ortho position is C-2.

''The ortho position is C-11.

'The oHho position is C-6. 'The para position is C-4. ^The ortko position is C-5. "The para position is C-1.

In angular hydrocarbons that contain no such anthracene moiety but which have a phenanthrene moiety in which C-9 and C-10 are not fused to another ring, it was predicted that one of these atoms would be the most reactive.

9 10

Phenanthrene Chrysene Benzo[£] phenanthrene Picene

For hydrocarbons having more-condensed ring-systems, the most reactive position preTriphenylene Pyrene Benzo [_e ] pyrene Perylene

13
dieted is adjacent to a point of ring fusion and may be regarded as that of a naphthalene

moiety.

In practically all cases that have been studied experimentally, the positions predicted

for one-center attack are those actually found. Thus, benzoyl peroxide attacks the most

reactive center of benz [a] anthracene and benzo [a] pyrene

Benz[a]anthracen-7-ol benzoate Benzo[a]pyren-6-ol benzoate

The reactivity of the reactive center of the linear hydrocarbons progressively increases

[9] ; that is, addition of each ring causes an increase in reactivity at the reactive center, in

the order naphthalene < anthracene <naphthacene<pentacene, and, as may be seen from

table 5, the localization energy of the most reactive center progressively decreases.

4.2. para Reactive Centers

In reactions involving tv^^o-center attack in which the two centers are para to each

other, use is made of the para-localization energy, that is, the energy required for simultaneously localizing an electron at each of the two positions considered. The para-localization energies for the various possible positions in some alternant hydrocarbons have been

calculated by Brown [10] and Dewar [8]. The para positions predicted to be the most re- active are listed in table 7, from which it may be seen that they are those to be expected

from the predictions given in table 6. For the linear hydrocarbons, the reactivity of para centers increases as the middle of

the molecule is approached. Also, the localization energy for the most reactive pair of para

centers decreases with increasing size of the molecule; that is, the relative reactivity

increases. The reactivity of the para centers in nonlinear hydrocarbons is always lower

than that of the corresponding linear hydrocarbons.

In all cases that have been studied, these predictions of para reactive centers agree

with those actually found.

4.3. ortho Reactive Centers

Although the structural formula of a polycyclic, aromatic hydrocarbon is normally

written with single and double bonds, pure single bonds and pure double bonds are actually

not present in the compound. The structural formula depicts an extreme resonance form,

and is not an accurate representation of the electronic configuration of the molecule ; each

carbon-carbon bond possesses some degree of double-bond character. Thus, in the same

molecule, two "double bonds," usually depicted as alike, may differ in reactivity. Furthermore, a "double bond" situated at a superficially similar position in two different hydrocarbons may have a different reactivity in each.

In considering reactions involving two-center attack at adjacent carbon atoms, use has been made of the ori/io-localization energy, that is, the energy required for localizing

14
Table 7. The most reactive para positions

(predicted) for some alternant hydrocarbons

Hydrocarbon

Most reactive para

positions predicted

»

Linear Naphthalene

Anthracene Naphthacene

Pentacene Hexacene

Angular

(a) Reactive anthracene moiety

Benz[a]anthracene

Benzo[a]naphthacene

Pentaphene

Benzo[6]chrysene

Dibenz[a, c]anthracene . . Dibenz[a,yianthracene

Dibenz[a, /i]anthracene

(b) Nonreactive phenanthrene moiety

Phenanthrene

Chrysene

Benzo[c]phenanthrene

Picene Condensed ring systems

Triphenylene

Pyrene

Perylene

1,4b

9,10"

5,12'>

6, 13b 6,15

7,12b

8,13b

5,14b

7,12

9,14b

7,14b

7,14b

[l,4]b,. [1,4]«

[1,4]« [l,4]o

[1,4]<

'By R. D. Brown, J. Chem. See. 1950, 691. "By M. J. S. Dewar, J. Am. Chem. Soc. 74, 3357 (1952).

""Not reactive.

an electron at each of the two carbon atoms involved. This energy might thus be regarded

as the energy required for converting the conjugated, aromatic bond into a pure double

bond. Alternatively, it is the energy needed for localizing a pure double bond between the

two carbon atoms ; indeed, it is often referred to as the "bond-localization energy." The

ori/io-localization energy can be estimated from the difference between the resonance en- ergy of the hydrocarbon and that of the residue which would be left on removal of the two

ortho carbon atoms under consideration. The smaller the or^/io-localization energy, the

more reactive is the bond.

By application of these principles. Brown [11] has calculated the reactivities of the

carbon-carbon bonds in each of a number of alternant hydrocarbons, and thence has predicted the most reactive bond in each. The results are given in table 8, together with predictions made by Dewar [8] by the molecular-orbital method, from which it may be seen

that, for all of the hydrocarbons having a phenanthrene moiety whose C-9 and C-10 atoms

are not fused to another ring, these two atoms were predicted to be the most reactive ortho

pair. For the other hydrocarbons, a bond corresponding to the 1,2-bond of naphthalene was predicted to be the most reactive.

Because of the difference in the electronic configurations necessary for reactions involving (a) one-center attack and (b) two-center, ortho attack, the ortho positions listed

in table 8 as the most reactive do not necessarily include the most reactive centers or even

the next most reactive centers (given in table 6), although a reactive center is often one

of the atoms involved with a reactive bond. Thus, if the most reactive center is indicated

by I, and the next most reactive center by II, the hydrocarbons can be classified in six

groups as regards the adjacent carbon atoms predicted to be those subject to ortho attack.

15
Table 8. The most reactive ortho positions

(predicted) for some alternant hydrocarbons

Hydrocarbon Most reactive ortho positions predicted ^

Linear Naphthalene

Anthracene

Naphthacene

Pentacene

Nonlinear

(a) Naphthalene moiety

Triphenylene

Dibenz[a, c]anthracene . . . (b) Phenanthrene moiety

Phenanthrene

Benz[a]anthracene

Chrysene

Benzo[c]phenanthrene. . . . Pyrene

Benzo[a]naphthacene

Pentaphene

Benzo[/>]chrysene

Dibenzo[6 , gtjphenanthrene

Dibenz(a,j]anthracene . . . Dibenz[a,A]anthracene. . . Picene

Benzo[g]chrysene

Benzo[c]chrysene

Dibenzo[c, g;]phenanthrene

Benzo[o]pyrene

Benzo[e]pyrene

1,2b

1,2"

1,2

1,2

1,2"

10, lib

9,10"

5,6"

5,6"

5,6"

4,5"

5,6"

6,7"

5,6

7,8

5,6"

5,6"

5,6

9,10

7,8

1,2

4,5

4,5"

•By R. D. Brown, J. Chem. Soc. 1950, 3249. "By M. J. S. Dewar, J. Am. Chem. Soc. 74, 3357 (1952).

These groups are those hydrocarbons involving (1) two I, as for phenanthrene; (2) I and

II, as for naphthalene and triphenylene; (3) II and II, as for pyrene; (4) I and the posiPhenanthrene Naphthalene Triphenylene

tion ortho to it, as for chrysene, benzo[c] phenanthrene, and picene; (5) II and the position

ortho to it (because a double bond including position I would obviously not be susceptible

Pyrene Chrysene Benzo[£] phenanthrene Ptcene

16
to ortho attack), as for anthracene, naphthacene, dibenz [a,c] anthracene, and dibenz[a,^]-

u

Dibenz anthracene Dibenz [ a,h] anthracene

anthracene; and (6) neither I nor II, as for pentacene, benzo[e]pyrene, benz [a] anthracene, benzo [a] naphthacene, pentaphene, and dibenz [a,/] anthracene.

Benzo[ a] naphthacene Pentaphene Dibenz [a^J^] anthracene

For all cases that have been studied, the positions predicted for ortho attack agree

with those found experimentally.

Brown [11] also calculated the reactivity of the most reactive bond in each of these

hydrocarbons, relative to that of the 9,10-bond of phenanthrene (which was arbitrarily

assigned the value of unity). The results are given in table 9, the hydrocarbons being

listed in order of increasing reactivity of the most reactive bond.

The most reactive bond predicted for naphthalene is at C1-C2 [12], and this has been

confirmed experimentally [13,14]. However, the relative reactivity for the C1-C2 bond of

17
Table 9. Most reactive bond (predicted) and

calculated relative 7-eactivity thereof, for some polycyclic, aromatic hydrocarbons"

Most reactive Relative reactivity (calcd) bond (predicted)

RRI Hj'drocarbon No.

No. bond Total

5256 1,2 6 A1 V 10~7 /S 1\J 6381 10, 11 2 0 0002.: 0 0001^ 3618 Anthracene 1,2 4 0. OOlg 0 007 5252 Na[>hthacene 1,2 4 0 09 6376 Pentacene 1 2 4 0 0055 0.02

6385 Benzo[{7]chrysene 9, 10 1 0 008r 0 OOQ

5254 Chrysene 5,6 2 fl 04, 0 OQ 6384 5^6 2 0 no 0 9 5255 Benzo[c]phenanthrene 5,6 2 0. 10 0.2

6387 Dibenzo[c , ^Jphenanthrene 1,2 2 0.2 0 4 6386 Benzo[c]chrysene 7,8 1 0.22 0.4 6379 Benzo[/)]chrvsene 5,6 1 0.33 0 6380 Dibenzo[6 , gjphenanthrene 7,8 1 0. 72 0 8 6400 Benzo[clpvrene 4,5 1 <r <l'

3619 Phenanthrene 9,10 1 1 000 1 5262 4,5 2 1.6 3 6383 Dibenz[a, /i]anthracene 5,6 2 2.4 5 5,6 2 2.9 6 5253 Benz[a]anthracene 5,6 1 5.1 5 6377 Benzo[a]naphthacene 5,6 1 8.0 8

6399 Benzo[a]pvrene 4,5 1 12 12 6378 Pentaphene 6,7 1 18 18

"From R. D. Brown, J. Chem. Soc. 1950, 3249.

Table 10. Predicted," and observed, relative rate constants'" for the addition of osmium tetroxide-pyridine to some polycyclic,

aromatic hydrocarbons

Relative rate constant RRI Relative Total No. Hj'drocarbon reactivity of relative reactive bond reactivity Predicted Observed

6386 Benzo[c]chrvsene 0.22 0.4 0.06 slow 3619 Phenanthrene 1.00 1 0.2 0.1 5253 Benz[ajanthracene 5.1 5 1 1 6383 Dibenz[a, /ijanthracene 2.4 5 1 1.3 6399 Benzo[a]pvrene 12 12 2 2.0

'R. D. Brown, J. Chem. Soc. 1950, 3249.

"G. M. Badger, J. Chem. Soc. 1949, 456; G. M. Badger and R. I. Reed, Nature 161, 238 (1948).

naphthalene is less than for anthracene; consequently, in hydroxylation with osmium

tetroxide-pyridine, a concentrated solution of this reagent was used (in order to provide

forcing conditions). Because addition to the C1-C2 bond gives a derivative that has, in

the nonbenzenoid ring, a double bond having a very small bond-localization energy, a sec- ond equivalent of osmium tetroxide reacts with this bond, affording a diadduct.

Similarly, addition of this reagent to the C1-C2 bond of anthracene would give a

product, related to 2-vinylnaphthalene, having an exocyclic bond of very low bond-localization energy, and it was to be expected that this bond would react with a second equivalent

of the reagent, affording a diadduct. This has been found experimentally [5]

.

For phenanthrene, the relative reactivity of the 9,10-bond is much higher than that

of the 1,2-bond of naphthalene and anthracene; this greater reactivity has been confirmed

experimentally [5,15,16].

18
Now, the rate of reaction found experimentally corresponds to the sum of the re- activity for all of the bonds in the hydrocarbon. For instance, the most reactive bond

occurs four times in anthracene, naphthacene, and pentacene ; this number is given in

column 4 of table 9. By multiplying the relative reactivity of the most reactive bond by

this factor, an estimate of the total relative reactivity was obtained (see column 6 of

table 9).

In table 10, five hydrocarbons are listed in their order of increasing (predicted)

total reactivity (relative to that of phenanthrene, arbitrarily assigned a value of unity),

together with the predicted rate constants (relative to benz [a] anthracene as unity) and

those actually observed for the addition of osmium tetroxide-pyridine (in chloroform at 20° C). As may be seen from table 10, the agreement between the predicted values and

those found experimentally was excellent.

4.4. Effect of Conformation of the Hydrocarbon

Until fairly recently, it had been assumed that all polycyclic, aromatic hydrocarbons

have a planar- conformation. In some of the studies on the oxidation of such hydrocarbons,

workers encountered certain supposed "anomalies" which are now explicable by taking

the correct conformation of the molecule into account.

It is now known that nonbonded carbon atoms do not generally approach closer

than 3.0 A, and that normal H-H distances are 2.4 to 2.5 A. For some polycyclic, aromatic

hydrocarbons, adoption of a planar conformation would necessitate compression of non- bonded atoms to well within this forbidden range. For example, it is seen that the protons

at C-4 and C-5 of phenanthrene, and those at C-1 and C-12 of benzo[c] phenanthrene

[17] , interfere with each other if the hydrocarbon has a planar conformation. This phePhenanthrene Benzo [£] phenanthrene

nomenon has been referred to as "molecular overcrowding."

Similarly, in benz [a] anthracene, there is crowding at C-1 and C-12.

Benz [ a ] anthracene

Relief of such a strain is, in some instances, obtained by adoption of a nonplanar,

stable conformation. This results in assumption, by certain atoms and bonds, of positions

in space that are different from those present in the planar conformation. As a conse- quence, the susceptibility of such atoms to oxidation may differ from that predicted by

calculations that ignore conformational effects. For example, in perylene, by the localiza19
tion theory, C-3 should have greater proton affinity than C-1. However, the two positions

Perylene

actually have almost identical affinities ; this is presumably because of added ease of distortion in the region at C-1 as compared with C-3.

In dibenzo[c,fif]phenanthrene, the region associated with C-10 and C-11 is very over12

9

Dibenzo [£,_g] phenanthrene

crowded; this is relieved [18] by displacements of atoms in a direction perpendicular to the mean plane of the molecule. The atoms on one side of the molecule are displaced upwards, and those on the other side are displaced downwards. For some atoms, the displacement is as much as 1.7 A.

4.5. Effect of Methyl Substituents

Methyl groups act as slight donors of electrons to aromatic compounds ; this causes

slight increases in the electron densities of the bonds and increases in bond orders, resulting in enhanced double-bond reactivity. The eects of methyl substituents on the reactivity of reactive centers, on para-localization energies, and on ort/io-localization energies

have been discussed [19].

The rate of reaction of osmium tetroxide-pyridine with polycyclic, aromatic hydrocarbons and their methyl derivatives is an excellent measure of the reactivity of the double bonds [13]. It was found that the methyl groups greatly affect the rate of oxidation;

moreover, the position of the methyl groups determines the magnitude of the effect. For benz [a] anthracene and its methyl homologs, the relative rate of reactivity of the

5,6-bond agreed with calculations of the effect of methyl groups thereon [20].

5. One-Center Attack

5.1. Oxidation Resulting in Substitution

In oxidation by substitution, the aromatic character of the attacked ring is preserved.

Substitution may be direct, as in the formation of phenols in some free-radical reactions

OH OAc OOH

o 6 - 6 6

20
[21]. However, in some substitution reactions, the reaction proceeds by way of an intermediate addition product which has been isolated [16, 22]. In other oxidations resulting in

substitution, the mechanism operating has not yet been determined.

Attack occurs chiefly at the most reactive center predicted (see table 6), although some molecules may be attacked only at the next most reactive center. For example, in

reactions of naphthalene with free radicals, substitution occurs mainly at C-1 only (see

table 11), but, simultaneously, some of the molecules are attacked at C-2 only.

Typical reagents are hydrogen peroxide in ultraviolet light, hydrogen peroxide cat- alyzed by ferrous sulfate (the Fenton reagent), benzoyl peroxide (see section 8.2.1), and

lead tetraacetate (see section 8.2.3).

Table 11. Proportions of 1 -substitution and

2-substitution products from reaction of naphthalene with free-radical reagents

Reagent Entering radical 1 -Isomer 2-Isomer References

Percent Percenl H2O2 (in U.V. light) OH 76 24 1 H202-FeS04 OH 79 21 1 (PhC02)2at 80° C PhC02 76 24 2 (PhC02)2 at 85° C PhCOs 73 27 3 (PhC02)2 at 100° C PhC02 68 32 3 (PhC02)2 at 100° C PhC02 88 12 4

References for table 11

1. E. Boyland and P. Sims, J. Chem. Soc. 1953, 2966.

2. R. Huisgen and R. Grashey, Ann. 607, 46 (1957).

3. D. I. Davies, D. H. Hey, and G. H. Williams, J. Chem. Soc. 1958, 1878.

4. B. M. Lynch and K. H. Pausacker, Australian J. Chem. 10, 165 (1957).

5.1.1. Oxidative Coupling In oxidative coupling, hydrogen abstraction from a reactive center affords a free

radical which can then react with another such free radical to give a dimer. The dimer

may now undergo hydrogen abstraction and coupling, and so on, resulting in the formation of a series of polymers.

In the first step, the hydrogen atom is removed directly, either by an oxy anion or by

a free radical (such as OH or HO2) produced by interaction of the oxidant with the sol- vent. Oxidative coupling is caused, for example, by benzoyl peroxide (see section 8.2.1).

6. Two-Center Attack

6.1. Addition to Two Reactive Centers

In this kind of oxidation, the net effect is attack at two carbon atoms which may be,

but are not necessarily, ortho or para to each other. The positions at which attack occurs can depend on the reagent and experimental conditions employed, as well as on the struc- ture of the hydrocarbon being oxidized. The localization-energy requirements for ortho as against para attack may not be directly comparable. Thus, according to the Pullmans [23]

,

whereas in an addition reaction at a bond, the decisive factor is the stability of the final

product, in addition reactions nonadjacent carbon atoms, the electronic characteristics of

the initial state have a greater influence.

6.1.1. para Addition Because of the increase in reactivity of the reactive centers of the linear benz-homologs as the series is ascended, there is a parallel increase in the ease of formation of addition compounds. Thus, anthracene reacts with nitrogen dioxide to give the 9,10-diadduct

21
(see section 9.1.7) and with oxygen in the light to give the 9,10-peroxide (see section

9.1.10) ; and, as the series is ascended, the product is more readily formed and is increasingly more stable.

6.1.2. ortho Addition In oxidation by addition to a "double" bond, transfer of oxygen atoms occurs, from an

oxygen-containing oxidant to the two carbon atoms at the ends of the bond, and the

aromatic character of the attacked ring is thereby removed.

In general terms, the reaction may be depicted as

H

The hydrocarbon furnishes two of its 7r-electrons, to form two new o--bonds between the

reagent and the hydrocarbon. Examples are given in section 9.2.1. Oxidants that may produce this result include the following: hydrogen peroxide plus

a catalyst, osmium tetroxide plus pyridine, and (perhaps) ozone. Because addition may be followed by elimination, a substitution product, such as might be obtained by a one-center attack, often results from ortho attack.

6.2. Oxidation to the Dione

If, in oxidation to a dione, the attack at the two carbon atoms were simultaneous, it should occur at the two atoms for which the combined localization energy is the minimum.

Now, oxidation of benz [a] anthracene (for example, with chromium trioxide) gives the

7,12-dione, despite the fact that the or^/io-localization energy calculated for C5-C6 is less

Table 12. Predicted diones, and those actually

obtained by the oxidation of polycyclic hydrocarbons

with chromium trioxide

Hydrocarbon Dione (predicted" and found)

Naphthalene

Anthracene

Naphthacene

Pentacene

Benz[alanthracene. . . Benzo[a]naphthacene

Pyrene

Phenanthrene

Chrysene

para

pseudo-para

ortho

1,4-

9,10-

5,12-

6,13-

7,12-

8,13-

1,6- plus 1,8-

9,10-

5,6-

'By M. J. S. Dewar, J. Am. Chem. Soc. 74, 3357 (1952).

22
than the para-localization calculated for C7,C12 [8, 11]. This suggests that an electrondeficient cation first attacks a single center, namely, that having the lowest localization

energy; then, attack occurs at that carbon atom which will afford the most stable dione.

The second point of attack is a center of equal reactivity (if there is one) or the next

most reactive center, although some oxidation may occur at the third most reactive center. The most reactive center and the next most reactive center for a number of hydrocarbons were listed in table 6. In all cases thus far examined, the positions predicted for two-center attack (see table 12) agree with those found experimentally.

Thus, for naphthalene, anthracene, naphthacene, and pentacene, oxidation occurs at two equally reactive centers, giving the p-dione. For benz [a] anthracene and benzo[a]-

naphthacene, reaction at the most reactive center and then at the next most reactive center

affords the p-dione indicated.

In phenanthrene, C-9 and C-10 are equally reactive centers ; oxidation occurs at these

to give the o-dione. Similarly, chrysene is oxidized at C-6, the most reactive center, and

then at C-5, to give the stable o-dione.

Phenanthrene (3619) Chrysene (5254)

In pyrene, C-1, C-3, C-6, and C-8 are equally reactive centers, and a mixture of the

1,6- ( = 3, 8-) and 1,8- ( = 3, 6-) diones is formed on oxidation with, for example, chromPyrene (5262) 1, 6-Pyrenedione 1,8-Pyrenedione

ium trioxide. No 1,3-dione would be expected, as it would be less stable than the other

diones.

Perylene has four equivalent, reactive centers, at C-3, C-4, C-9, and C-10, and the

Perylene (6401)

23
expected 3,10-dione is formed with chromium trioxide [24].

Dewar's predictions [8] indicate that, in benzo[a]pyrene, the most reactive center is

/

3

b

Benzo[^]p)rrene (6399)

at C-6, the next most reactive center is at C-1, and the third most reactive center is at C-3. This explains why, by the action of appropriate oxidants, benzo [a] pyrene gives a mixture of the 1,6-dione with the 3,6-dione.

7. Pre-oxidative Behavior

A knowledge of the behavior to be expected of polycyclic, aromatic hydrocarbons in

certain environments p7'ior to occurrence of oxidation is helpful in understanding the

mechanisms involved when oxidation does take place.

7,1. With Oxygen

In 1937, Sklar [25] observed, in the ultraviolet absorption spectrum of benzene ex- posed to the air, certain bands which he ascribed to a singlet-triplet transition. These

bands (at about 312, 321, 330, and 340 m/x) were also observed by subsequent workers

[26] . However, it remained for Evans [27] to discover that these bands disappear when

the dissolved oxygen is removed, but reappear (and are stronger) when the benezene is saturated with oxygen. The same phenomenon was observed with naphthalene and other

polycyclic, aromatic hydrocarbons [28]. Nitric oxide (NO) has a similar effect, and it was pointed out that both oxygen and nitric oxide are both paramagnetic and electronaccepting. Evans concluded that the effect is largely due to the paramagnetic effect of

the oxygen molecule, but that charge transfer might play some part. Other workers [29]

have considered that the enhancement of the singlet-triplet absorption bands is due to charge transfer in which oxygen is the electron acceptor and the hydrocarbon (Z) is the

Z + O2

^ Z - O2

electron donor ; this explanation has now been accepted by Evans [30]

.

In related work, it has been found that oxygen quenches the fluorescence of many polycyclic, aromatic hydrocarbons [31-33] , and this effect, also, has been attributed [32] to formation of a charge-transfer complex of the hydrocarbon with oxygen. Nitric oxide also

quenches the fluorescence, and sulfur dioxide causes a decrease in intensity of the fluores- cence.

7.2. With Strong Acids

In 1940, Weiss [34] pointed out that any compound containing conjugated double

bonds should be capable of forming ions, particularly positive ions ; he described [35] the

formation of salts of anthracene, benzo [a] pyrene, benzo [a] perylene, and coronene with

perchloric acid, pyrophosphoric acid, and sulfuric acid ; for example

Anthracene pe^rchlorate

24
Thus, the hydrocarbons behave as bases in strongly acidic solvents [36], giving a proton

complex or carbonium ion, such as

e

It was found that a solution of perylene in concentrated sulfuric acid is paramagnetic

[37] , because of the formation of free radicals ; the electron spin resonance spectrum [38]

showed that singly charged, monopositive ions of perylene are formed. In oxygen-free

hydrofluoric acid (or hydrofluoric acid-boron trifluoride), the perylene is present as a

proton complex ; however, when oxygen gas is introduced, part of the protonated species

is converted into the monovalent, positive ion [39]. That is, in hydrofluoric acid, the

aromatic hydrocarbons (Z) behave as bases ; when the aromatic hydrocarbons are dissolved in strongly proton-active and oxidizing media, they give proton complexes and

Z + HF ZH^ + f"

positive ions. Thus, solutions of anthracene in sulfuric acid [40] , or in hydrofluoric acid

plus oxygen, give both species [41].

Z + H.SO , ^=f^ ZH*" + HSO,

From a study of the action of oxygen on perylene dissolved in trifluoroacetic acid

[42], it was found that greater acidity of the solvent favors electron transfer, leading to the formation of a monopositive ion in the ion pair.

Z - O2

^

Z+ .02"

In addition, a solution of perylene in perchloric acid shows absorption bands (at 503

and 530 m/i), said to indicate the presence of a paramagnetic ion [43].

Such reactions are undoubtedly important in oxidations conducted in, or with, strong

acids.

7.3. With Ultraviolet Light (Non-oxidative Dimerization)

Under the influence of ultraviolet light, dimerization can occur ; although this is not

oxidative, since hydrogen abstraction is not involved, it is mentioned, as it may be en- countered in such studies.

Fritzsche [44] found that, if a cold, saturated solution of anthracene in benzene is kept in sunlight, dimerization occurs, to give 9,9' :10,10'-bianthracene [45,46]; this is sparingly soluble and crystallizes out. On being melted, it is depolymerized to anthracene.

25
Solutions of anthracene in xylene, anisole, or phenetole, when boiled in the light, give the

dimer [45] ; but, if boiling is continued in the dark, the monomer is regenerated. Benz[a]-

anthracene behaves similarly.

Chloroform and carbon disulfide inhibit this dimerization [47] , but ether promotes it. The dimerization is attributed [48] to formation of excited diradicals of anthracene which

react with normal molecules of anthracene. To prevent formation of anthraquinone, oxygen must be excluded [49]

.

The self-quenching of fluorescence observed with irradiated solutions of polycyclic,

aromatic hydrocarbons has been attributed [32] to reaction of excited molecules (Z*) with

unexcited molecules (Z) to give molecules of a transient dimer; this is reversed in the

z + z -"T—— z z -K—— z_ dark dark 2

dark. Ordinarily, these dimers have very short lives [50]. For naphthalene in benzene,

the transient dimer is formed in 0.1 M naphthalene, but not below this concentration [33].

8. Agents Causing One-Center Attack

8.1. At an Active Methylene Group

8.1.1. Chromium Trioxide Chromium trioxide in hot, glacial acetic acid (or sodium dichromate in aqueous

sulfuric acid) oxidizes a reactive methylene group to a ketone group. For example,

S 2-

I II

Fluorene (3127) Fluoren-9-one

Acenaphthene (3133) Acenaphthenequinone Naphthalic acid

26
8.1.2. Lead Tetraacetate Lead tetraacetate, used in excess, oxidizes an active methylene group. For example,

Pb(OAc)

or PbO^'HOAc

Acenaphthene (3133)

1 -Acenaphthenol acetate

This reagent oxidizes fluorene to fluoren-9-one [51].

8.1.3. Oxygen

In pyridine, in the presence of benzyltrimethylammonium hydroxide, fluorene is oxidized by oxygen to fluorenone at room temperature [52] ; the reaction is not sensitive to

light.

1,4-Dihydronaphthalene is oxidized by oxygen to the hydroperoxide [53] and other

products.

1 ^4-Diliydro-l-naphthyl hydroperoxide

8.1.4. Oxygen and Ultraviolet Light

On treatment with oxygen and ultraviolet light for 30 hr at 70° C, fluorene in benzene

gives the stable 9-fluorenyl hydroperoxide [54].

8.1.5. Ozone

Ozone oxidizes fluorene to fluoren-9-one [51].

8.1.6. Selenium Dioxide

Selenium dioxide in hot acetic acid or acetic anhydride may oxidize an active methylene

group to a carbonyl group. For example, fluorene gives fluoren-9-one [55] in 65 percent

yield.

27
Acenaphthene, in the absence of solvent, gives [56] a mixture of acenaphthylene and

cis- and trans - 1,2-

Acenaphthene (3133) Acenaphthylene Acenaphthenediol

the cis- and tmns-l,2-acenaphthenediols. With acetic acid as the solvent, it gives, in addition to these products, a polyacenaphthylene and a binaphthylenecyclobutane [57]

.

8.2. Oxidation of One Reactive Methylidyne (Methine) Grouping

8.2.1. Benzoyl Peroxide (a) Substitution. On treatment of naphthalene with benzoyl peroxide at 85° C, the

principal reaction is nuclear benzoyloxylation [58] at C-1 and, separately, at C-2 by

benzoyloxy radicals, giving naphthyl 1- and 2-benzoates in the ratio 73:27 (see table 11).

The substitution consists of addition of the benzoyloxy radical, followed by elimination of a hydrogen atom. (Side reactions leading to phenylation and to oxidative coupling are

discussed in section 8.2.1b.)

The relative reactivity of C-2 is raised [58] by increasing the reaction temperature to 100° C; simultaneously, the main reaction (banzoyloxylation) decreases, and phenylation

increases.

(b) Oxidative coupling. Benzoyl peroxide gives rise to benzoyloxy radicals [59] and

to phenyl radicals.

PhCO-O-O-COPh ,^ 2 PhCO-0»

PhCO-0« ^—

Ph* +

In the reaction of benzoyl peroxide with naphthalene [58], the benzoyloxy radicals

act in two ways: (a) by direct substitution to give naphthyl 1- and 2-benzoates (see sec- tion 8.2.1a), and (b) by hydrogen abstraction, followed by dimerization, to give binaphthyls in the ratio of 54:42:4 for the 1,1'-, 1,2'-, and 2,2'-isomers.

The free phenyl radicals cause nuclear phenylation at C-1 and C-2 (giving an 82:18

mixture of 1- and 2-phenylnaphthalenes).

28
8.2.2. Hydrogen Peroxide Catalyzed by Osmium Tetroxide This reagent oxidizes naphthalene to give, in part, 1-naphthol (see table 3). Similarly,

phenanthrene gives, in part, 9-phenanthrol. It is probable that the diol is first formed (see

section 9.2.1 (1) ), and that this undergoes dehydration.

CH 'OH

II ^

CH

I

8.2.3. Lead Tetraacetate In the reaction of lead tetraacetate with anthracene in benzene at 35 to 55° C, a mixture of the cis and trans diadducts is formed [60]

.

I 1 HOCH (- H^O) HOC

I 2 ^ II HOCH CH

Used hot, this reagent causes acetoxylation of some aromatic hydrocarbons. Thus,

with anthracene, the acetate of 9-anthrol and that of 10-hydroxyanthrone are formed

[60] , the mechanism probably involving addition of an acetoxyl group to each reactive

center, followed by elimination, as shov^m. Similarly [61] , but not necessarily by the same

mechanism.

Instead of lead tetraacetate, red lead oxide plus glacial acetic acid was originally used.

A similar mixture of acetates was produced from anthracene by the action of eerie acetate,

manganese dioxide, stannic oxide, or vanadium pentoxide in glacial acetic acid [60,62].

29
8.2.4. Oxygen and Ultraviolet Light

Treatment of 2a,3,4,5-tetrahydroacenaphthene with oxygen and light for 150 hours

at room temperature gives the hydroperoxide [63].

q5

8.2.5. Peroxybenzoic Acid

On oxidation of dibenz [a,/^] anthracene with peroxybenzoic acid [64], a 7.3-percent

yield of 7,14-dihydrodibenz[a,/i]anthracen-7-one is obtained, presumably via intermediate

formation of the 7,14-epoxide.

DibenzCa, h]anthracene (6383) 7, 14-Dihydrodibenz [a , h ]anthracen- 7 -one

Pyrene gives a mixture [65] of 1- and 4-pyrenols, as well as other products (see sec- tions 9.1.8 and 9.2.1 (4)).

9. Agents Causing Two-Center Attack

9.1. At Two, Nonadjacent, Methylidyne (Methine) Groupings

9.1.1. Benzoyl Peroxide Benzoyl peroxide attacks anthracene to give anthraquinone. Similarly, dibenz [a,/i]

anthracene gives the 7,14-dione (see table 3).

9.1.2. Chromium Trioxide On oxidation with chromium trioxide in glacial acetic acid (or dichromate in sulfuric

acid), two nonadjacent methine groups may give the corresponding dione (see table 3). For some of the hydrocarbons (e.g., naphthalene, anthracene, benz [a] anthracene, and dibenz-

[a,/i] anthracene), this product is the p-dione. However, for benzo [a] pyrene, which lacks

any para pair of reactive centers, a mixture of the 1,6-dione and 1,8-dione is formed.

9.1.3. Hydrogen Peroxide Catalyzed by Osmium Tetroxide By use of the Milas reagent (see section 9.2.1 (1) ), two nonadjacent methine groups

30
may be oxidized to the corresponding dione. Thus, anthracene is attacked exclusively at C-9 and C-10, the reactive centers, to give anthraquinone (see table 3).

In some instances (see table 3), this reagent affords two series of products [65a] ; one

results from attack at nonadjacent centers, and the other from addition to a reactive bond

(see sections 9.1.3 and 9.2.1 (1) ). The two attacks appear to be simultaneous, but the relative proportions of the products depend on the relative reactivities of these two sites of

attack.

By comparison of the respective behavior of anthracene, benz [a] anthracene, and

dibenz [a,/i] anthracene, the effect (on these reactivities) of nonlinear addition of a benzene

ring was ascertained. Whereas anthracene reacts solely at the reactive para centers, benz-

[a] anthracene reacts in both ways; it gives the 7,12-dione by attack at the nonadjacent,

II 0

Benz [a] anthracene-7, 12-dione

reactive centers, but it also gives the 5,6-diol (see section 9.2.1 (1)), a smaller proportion

of the 5,6-dione (see section 9.2.3 (2)), a small proportion of 3-(o-carboxyphenyl)-2-

naphthoic acid (from ring-scission of the 5,6-dione), and some phthalic acid.

In contrast, dibenz [a,/i] anthracene gives mainly the 5,6-dione, by reaction at the 5,6-

bond (see table 3). Thus, addition of one benzene ring to anthracene raises the reactivity

of the reactive bond and lowers the reactivity of the nonadjacent reactive centers; and

addition of a second ring enhances these two effects even more, so that the 5,6-bond be- comes the most reactive part of the molecule.

9.1.4. Lead Tetraacetate With 2 molar proportions of lead oxide in hot glacial acetic acid, anthracene is oxidized to 10-hydroxyanthrone acetate [60,62]

.

9.1.5. Nitric Acid

Whereas dilute nitric acid adds to C-9 and C-10 of anthracene [66], concentrated

0

nitric acid gives anthraquinone [67] . Nitrates, oxides of nitrogen, and nitrites have also

been used, under a variety of conditions, for oxidation of anthracene to anthraquinone

(see table 13).

31
In hot, glacial acetic acid, nitric acid acting on anthracene causes both (a) dimerization, and (b) oxidation to the ketone [68].

O

0

10, 10 ' -Bianthrone

Table 13. Oxidation of anthracene to anthraquinone

by action of nitric acid, nitrates, oxides of nitrogen, or nitrites"

Reactant and conditions

Liquid nitrogen dioxide Nitrogen dioxide in acetic acid Nitrogen oxides in water or ethanol .

.

Nitrogen dioxide in benzene

Nitrogen oxides in nitrobenzene Nitrogen dioxide in presence of mercuric nitrate, in nitrobenzene at 100-110° C

Nitrogen dioxide and air, at 200° C

Nitrogen dioxide and air, or nitric oxide and air, at 200° C

Ditto (in presence of zinc dust or lead oxide, to neutralize nitric acid) Air and ZnO or CuO treated with NO2, at 250-300° C

Nitrogen dioxide and air, anthracene mixed with pumice or asbestos (to minimize nitration) Nitrogen oxide in presence of Zri compounds or Cu oxides Oxygen plus small proportion of nitrogen oxides or fuming HNO3, in presence of cobalt nitrate in acetic acid or other solvent, at 80-90° C.

Nitric acid in nitrobenzene-acetic acid, in presence of mercuric nitrate Oxygen, catalyzed by nitric acid, oxides of nitrogen, or nitrites (liquid phase)

Sodium nitrate plus MgCl2-6H20 at 210° C

Sodium nitrite in acetic acid-acetic anhydride, with oxygen under pressure at 90° C

'Only references to early work are given.

References for table 13

1. P. F. Frankland and R. C. Farmer, J. Chem. Soc. 79, 1356 (1901).

2. A. Glaus, Ber. 10, 925 (1877). A. R. Leeds, J. Am. Chem. Soc. 2, 416 (1880).

3. P. S. Varma and J. L. D. Gupta, J. Indian Ghem. Soc. 4, 296 (1927).

4. L. W. Bass and T. B. Johnson, J. Am. Ghem. Soc. 46, 456 (1924).

5. Badische Anilin und Soda-Fabrik, Ger. Pat. 268,049 (1909); Chem. Abstr. 8, 2067. M. A. H'inskii, B. V. Maksorov, and N. V. Elagin, Zh. Khim. Prom. 5, 469 (1928).

6. Ghem. Fabrik Griesheim-Elektron, Ger. Pat 284,179 (1914); Chem. Abstr. 10, 122.

7. J. Wetter, Brit. Pat. 16,312 (1910).

8. Chem. Fabrik Gruenau Landshoff and Meyer, Ger. Pats. 234,289 (1908), 254,710 (1910); Ghem. Abstr.

5, 2941; 7, 1266.

9. Farbw. vorm. Meister Lucius and Bruening, Ger. Pat. 256,623 (1911); Ghem. Abstr. 7, 2479.

10. Ghem. Fabrik Gruenau Landshoff and Meyer, Ger. Pat. 215,335 (1908); Ghem. Abstr. 4, 677.

11. Farbw. vorm. Meister Lucius and Bruening, Ger. Pat. 292,681 (1914); Ghem. Abstr. 11, 1554.

12. Ghem. Fabriken Worms, Ger. Pats. 406,245 (1918), 406,777 (1919); Ghem. Zentr. 96, I, 1133 (1925).

13. Chem. Fabrik Griesheim-Elektron, Ger. Pats. 283,213 (1913), 284,083-4 (1914); Chem. Abstr. 9, 2599,

10, 122.

14. A. Ullrich, U. S. Pats. 1,466,683 (1923), 1,467,258 (1923); Chem. Abstr. 17, 3878. Chem. Fabriken

Worms, Brit. Pats. 156,215 (1921), 156,538 (1921); Chem. Abstr. 15, 1726; Brit. Pat. 169,145 (1921);

Chem. Abstr. 16, 424.

15. K. A. Hofmann, Ger. Pat. 277,733 (1913); Chem. Zentr. 85, II, 899 (1914). K. A. Hofmann, F. Quoos,

and 0. Schneider, Ber. 47, 1991 (1914).

16. Chem. Fabriken Worms, Ger. Pat. 350,494 (1919); Chem. Zentr. 93, II, 1142 (1922).

References

12

3

45

6

78

910 8,10

1112

1314

1516

32
9.1.6. Nitric Oxide and Ultraviolet Light

When a solution of naphthalene, irradiated with ultraviolet light, is exposed to nitric

oxide, the hydrocarbon is excited to the triplet state, and the diradical reacts with the nitric

oxide [69].

9.1.7. Nitrogen Dioxide (Addition)

Anthracene reacts with nitrogen dioxide to give 9,10-dihydro-9,10-dinitroanthracene.

Anthracene

By further action (or with nitric acid), two other products are formed.

0

9.1.8. Organic Peroxy Acids

Peroxyacetic acid (or hydrogen peroxide in acetic acid) may attack nonadjacent

methine groupings, as for naphthalene, anthracene benz [a] anthracene, and pyrene (see

table 3), to give the corresponding dione. Thus, with peroxyacetic acid, anthracene gives

anthraquinone [70]. Similarly, with this reagent, benz [a] anthracene gave [71] the 7,12-

dione as the sole product. The same dione was obtained by use of peroxybenzoic acid [72]

.

Under more drastic conditions, peroxyacetic acid gave [73], in addition to the 7,12-dione, some 3-(o-carboxyphenyl)-2-naphthoic acid.

Pyrene, oxidized with peroxybenzoic acid, gives a mixture [65] of the 1,6- and 1,8-

diones, as well as other products (see sections 8.2.5 and 9.2.1 (4) ).

9.1.9. Oxygen

Fritzsche [6] found that, when solutions of anthracene are kept for a long time in

flasks open to the air, anthraquinone crystallizes out. The same reaction proceeds more

rapidly [74] with oxygen under pressure at 210-260° C. On treatment with oxygen for 430 hr at 18° C, 1,2-dihydronaphthalene gives the unstable pa^^a transannular peroxide [75], among other products (see section 9.2.1 (3)).

This peroxide rearranges to a trimer.

CO —

33
Indene, treated with oxygen for 100 hr at 25° C, allegedly gives, among other products, an unstable, meta transannular peroxide [54,76] which rearranges to a trimer.

Hi

c

11

-o

"2- n

-"3

However, according to Russell [77] , the structure of the polymeric peroxide is OH

9.1.10. Oxygen and Ultraviolet Light (Transannular Addition)

On treatment with oxygen while being irradiated with sunlight or ultraviolet light,

anthracene gives a photo-oxide [78] if the solvent is carbon disulfide ; but, if the solvent

is benzene, bianthracene is formed [44] (see section 7.3).

In 1930, it was shown [79] that, for pentacene, the photo-oxide has a transannular

structure, and it has since been found that this is the general structure for such photooxides. Thus, for anthracene, a molecule of oxygen is added [78,80] , across the central

10

Anthracene (3618) 9^10-Dihydro-9,10-epidioxyanthracene

ring (from C-9 to C-10), to give the 9,10-peroxide. Naphthacene [81] and pentacene are photo-oxidized more readily, and the reaction occurs so readily with hexacene [82] and

heptacene that solutions of these hydrocarbons, exposed to air and light, are almost instantaneously photo-oxidized. The ease of formation of the photo-oxide is related to the

triplet-energy level of the excited species. The nonlinear hydrocarbons react, with oxygen, less readily than the linear polyacenes, or not at all. The oxygen molecule has two unpaired electrons and is a diradical. Under the action

:0 0; or •0-0«

# •

34
of ultraviolet light, transannular addition of oxygen occurs at the most reactive centers of

linear aromatic hydrocarbons having two reactive centers that are para to each other, as

in the anthracenoid hydrocarbons, giving transannular peroxides. Electronically excited

molecules of the hydrocarbon take part in the addition, and the triplet state is involved.

It seems probable that the absorbed light excites the dienoid structure to a diradical which

then rapidly reacts with the oxygen diradical. The overall process involves consumption

XC XX 0-0'

of diradicals with no regeneration ; hence, these are not chain reactions.

The transannular addition of oxygen is facilitated by the presence of electron-donating substituents (e.g., methyl or phenyl) at the reactive centers; thus, 9,10-dimethoxyanthracene is readily photo-oxidized [83] . Addition is retarded by such electron-attracting

groups as carboxyl and cyano at these centers. Many of the*photo-oxides dissociate on heating, with liberation of oxygen; the extent

of the dissociation depends on the nature of the substituents. Thus, the photo-oxide of

5,6,11, 12-tetraphenylnaphthacene (rubrene) [84] and those of the 9,10-diarylanthracenes

readily dissociate on heating, to give the original hydrocarbon plus free oxygen [78,85]

;

the photo-oxides of the lO-aryl-9-methylanthracenes liberate less than 50% of their oxygen on being heated ; and the 9-alkyl- and 9,10-dialkyl-anthracene photo-oxides do not lib- erate oxygen.

If a sublimed film of anthracene is treated with dry oxygen and ultraviolet light

(3650 a), it is unchanged. However, if the sublimation is conducted in dry oxygen, under

the same irradiation, onto a plate at —180° C, there occur slight, temperature-dependent,

spectral changes which were attributed [86] to formation of a loose adduct of anthracene

with oxygen. On the other hand, if the latter sublimation is performed in moist oxygen,

the irradiated anthracene reacts immediately to give a product, having the spectrum of a

cyclic photo-oxide, which is changed to a more stable form by warming to —150° C and

recooling to —180° C [87]. This stable form is also obtained by sublimation, m t/ie darfc,

of anthracene onto a plate at —180° C, in moist oxygen. Tetracene and benz [a] anthracene

do not exhibit this behavior.

9.1.11. Oxygen and Ultraviolet Light, with Catalysts

During the chromatography of benzene solutions of anthracene on columns of alumina,

oxidation of part of the hydrocarbon to anthraquinone was observed [88] ; the oxidation was attributed to oxygen adsorbed on the surface of the alumina [89] . However, it was

pointed out [90] that the oxidation does not occur in the dark, and so photo-oxidation is involved.

If anthracene adsorbed on alumina is exposed to ultraviolet light, anthraquinone is formed, together with alizarin (1,2-dihydroxyanthraquinone), quinizarin (1,4-dihydroxy35
anthraquinone), and chrysazin (1,8-dihydroxyanthraquinone) [91].

Anthraquinone Alizarin

Quinizarin Chrysazin

The relative proportions of the products depend to a large extent on the pretreatment

given the adsorbent. Naphthalene on alumina gives 1,2-naphthoquinone only. Oxidation

was also observed on other adsorbents. On zinc oxide, only anthraquinone was obtained

from anthracene. Silica gel was found to be particularly effective [92] , giving a 50 percent yield of anthraquinone from anthracene after 1 hr of ultraviolet irradiation ; oxidation was much slower on magnesium oxide or potassium chloride, and 10 hr of irradiation on alumina gave a 10 percent yield of quinizarin.

It was supposed [93] that, in the absence of oxygen, a carbonium ion is formed by

transfer of a proton from silica-alumina to C-9 of the anthracene ; when oxygen is present,

this ion is oxidized. Hence, the role of the silica-alumina is that of a catalyst. Other studies

[94] have shown that interaction of the hydrocarbon with protonic acid sites on the cat- alyst give a hydrocarbon-proton complex ; electron transfer from this complex to oxygen

affords a positive radical-ion of the hydrocarbon. However, in the absence of oxygen,

anhydrous silica-alumina or zeolites give a positive radical-ion of the hydrocarbon on the

catalyst by transfer of a single electron from the hydrocarbon to an acid site on the

catalyst [38b,c,95]. Stable carbonium ions of polycyclic, aromatic hydrocarbons are obtained [96] by irradiating a mixture with silica gel (or silica-alumina) at —78° C with

cobalt-60 y-radiation for 1 hr.

9.1.12. Oxygen with Various Catalysts

With air over vanadium pentoxide at 300 to 500° C, two nonadjacent methine groups

may afford the corresponding dione; thus, anthracene gives anthraquinone (see table 14).

Similarly, pyrene [97] gives a mixture of the 1,6-dione and the 1,8-dione.

According to Senseman and Nelson [98], the vanadium pentoxide is reduced to a lower oxide of vanadium, and this is then re-oxidized to the pentoxide by oxygen.

Various catalysts used for liquid-phase or vapor-phase oxidation, with air or oxygen,

of anthracene to anthraquinone, are given in table 14. Because of the alternate reduction and oxidation of the oxide, only oxide catalysts

consisting of oxides of metals having more than one degree of oxidation, and capable of

ready reduction to a lower oxide and reoxidation to a higher oxide, are effective.

36
Table 14. Oxidation of anthracene to anthraqidnone, in the

liquid or vapo-r phase, with air or oxygen plus a catalyst'

Conditions

Liquid phase

Vanadium compounds are more active than chromium compounds, in liquid suspension

Susfjension in aqueous FeS04 solution In acetic acid, plus osmium tetroxide, at 10 atm at 50-100° C

In p^Tidine, or dispersed in aqueous alkali, in presence of Cu, Co, Xi, or Pb compounds as

catalysts. In pjTidine or aqueous ammonia, or without CuO or CuS04'5H20, at 170° C

In acetic acid, under pressure, in presence of copper vanadate or ammonium vanadate at 100-120° C or 160° C.

Vapor phase

(a) Over vanadium pentoxide Oxides of metals of the oth and 6th group of the Periodic Table, particularly vanadium pento.xide. . Vanadium oxides, or vanadate, on pumice

Ditto, mixed with moist carbon dioxide gas Vanadium oxides plus oxides of other metals, on pumice or asbestos Vanadium oxides plus molybdenum oxides

(b) Over other catalysts Coal or peat Oxides of chromium, molybdenum, tungsten, or uranium, at 500° C

A contact mass containing boric acid, at 400-430° C

Crushed firebrick mixed with phosphoric acid, at 380-400° C

Zeolites containing combined vanadium

Arsenates, chromates, molybdates, stannates, uranates, or vanadates of cerium, cobalt, copper,

lead, nickel, silver, or thorium. Titanium oxide (on pumice) pretreated with 2% (by volume) of nitrogen o.xides, at 400-500° C. . . .

'Only references to early work are given.

References for table 14

1. G. Witz, Compt. Rend. 83, 348 (1876); 87, 1087 (1878).

2. A. F. Poirrier and D. A. Rosenstiehl, Brit. Pat. 8431 (1887).

3. K. A. Hofmann, Ber. 45, 3329 (1912).

4. Farbw. vorm. Meister Lucius and Bruening, Ger. Pat. 292,681 (1914); Chem. Abstr. 11, 1554.

5. A. Wohl, Ger. Pat. 388,382 (1917); Chem. Zentr. 95, I, 2634 (1924).

6. J. Walter, Ger. Pat. 168,291 (1904); Chem. Zentr. 77, I, 1199 (1906).

7. J. M. Weiss and C. R. Downs, U. S. Pat. 1,355,098 (1920); Chem. Abstr. 15, 538. C. E. Senseman and

O. A. Nelson, Ind. Eng. Chem. 15, 521 (1923). A. Wohl, Ger. Pats. 347,610 (1916), 349,089 (1916);

Chem. Zentr. 93, II, 700, 946 (1922).

8. Badische Anilin- und Soda-Fabrik, Ger. Pat. 408,184 (1920); Chem. Zentr. 96, I, 1811 (1925).

9. C. Conover and H. D. Gibbs, U. S. Pat. 1,417,367 (1922); Chem. Abstr. 16, 2518.

10. A. E. Craver, U. S. Pat. 1,636,856 (1927); Chem. Abstr. 21, 3058.

11. M. Dennstedt and F. Hassler, Ger. Pat. 203,848 (1907); Chem. Abstr. 3, 586.

12. C. Conover and H. D. Gibbs, U. S. Pat. 1,303,168 (1919); Chem. Abstr. 13, 1863.

13. Badische Anilin- und Soda-Fabrik, Ger. Pat. 397,212 (1921); Chem. Zentr. 95, II, 1023 (1924).

14. Badische Anilin- und Soda-Fabrik, Ger. Pat. 419,861 (1921); Chem. Zentr. 97, I, 1713 (1926).

15. A. 0. Jaeger, U. S. Pats. 1,685,635 (1928); 1,786,950 (1930); Chem. Abstr. 22, 4536; 25, 716. Ind. Eng.

Chem. 20, 1330 (1928).

16. A. Wohl, Brit. Pats. 156,244-5 (1921); Chem. Abstr. 15, 1727. U. S. Pat. 1,787,416 (1930); Chem.

Abstr. 25, 716.

17. F. W. Atack, Brit. Pat. 182,843 (1921); Chem. Abstr. 16, 4214.

Anthraquinone was also prepared by passing a stream of air through an intimate

mixture of powdered anthracene and alumina for 48 hr at 120° C [99] ; fluorene gave

fluoren-9-one. By use of alumina pretreated with sodium methoxide, less drastic conditions (24 hr at 55° C) were effective.

9.1.13. Ozone

Ozone attacks anthracene predominantly by para addition to the reactive centers at

C-9 and C-10 [72,100]. With acetic acid as the solvent, a 70 to 75 percent yield of anthraquinone is obtained. Three equivalents of ozone are absorbed, and the initial product may

References

6

78

910

1112

1314

15

16

17

37
result from transannular addition, as in formation of the photo-oxide, to give I; alternately, the first product may be the 7r-complex, II. H

Either I or II could now give rise to III.

0-0'

0

II

H 00 H

II

^

0

II

n0

III

Hov^ever, this does not account for the absorption of three molar proportions of ozone ; a

small proportion of 2,3-naphthalenedicarboxylic acid is also formed [101], shovi^ing that

there is a much slower ortho attack at the reactive C1-C2 bond.

I 0,

Naphthacene behaves similarly [101,102].

Ozone, likewise, reacts with benz [a] anthracene by both ortho and para addition. By

treatment with one molar proportion of ozone [103], the main product was the 7,12-dione,

+

and a small proportion of 1,2-anthraquinonedicarboxylic acid was also formed. However,

by using different conditions [73,101,104], a 13 percent yield of the 7,12-dione and 11 percent of 3-(o-carboxyphenyl)-2-naphthoic acid was obtained. Use of 2 molecular proportions of ozone gave 17 percent of each of these. This indicates attack at the 5,6-bond, as well as at the 7,12-positions,

38
Whereas anthracene and naphthacene react mainly by para addition, naphthalene,

phenanthrene, chrysene, pyrene, and triphenylene react by ortho addition (see section

9.2.2(5) ). From a consideration of the resonance energies and redox potentials in relation

to the observed course of ozonization, it has been concluded [105] that ozone reacts preferentially at the positions which give the most stable ortho or para adduct as the intermediate.

However, the behavior of benzo [a] pyrene with ozone fits into neither category,

as this hydrocarbon lacks any para pair of reactive centers. With one molar proportion of

ozone, a 3:1 mixture of the 1,6-dione and the 3,6-dione is formed, together with a trace

of the 4,5-dione [106] . With larger proportions of ozone, rupture of rings occurs.

9.1.14. Selenium Dioxide Selenium dioxide, in the absence of solvent, oxidizes anthracene to anthraquinone in

76 percent yield [55a] ; with nitrobenzene as solvent, the yield is 73 percent [107].

9.1.15. Miscellaneous Reagents

A great variety of different oxidants have been used during the past hundred years

for the oxidation of certain of the polycyclic, aromatic hydrocarbons. Some of those used

for the oxidation of anthracene to anthraquinone are listed in table 15.

9.2. At a "Double" Bond

9.2.1. Addition to a "Double" Bond

(1) Hydrogen peroxide, catalyzed by osmium tetroxide. In a study of oxidation ef- fected by hydrogen peroxide, Milas [108] examined the effect of a number of catalysts,

including osmium tetroxide, vanadium pentoxide, and chromium trioxide. He found that a good solvent for the reaction is tert-hntyl alcohol.

Mugdan and Young [109] evaluated the various methods for hydroxylation with

hydrogen peroxide in the presence of catalysts, and decided that anhydrous hydrogen

peroxide catalyzed by osmium tetroxide, in tert-huty\ alcohol, is probably the best. This

"Milas reagent" probably contains tert-hutyl hydroperoxide, MegC-O-OH, which can, indeed, be used instead of the Milas reagent.

The active agent is the free hydroxyl radical, 'OH, and this reacts with a reactive

bond of some aromatic hydrocarbons to give a diol. For example, phenanthrene gives

I I CH ... HOCH

ii *0H ( CH HOCH

i I

9,10-dihydro-9,10-phenanthrenediol and benz [a] anthracene affords the 5,6-diol (see table

3) together with other products. In other instances, although the reaction undoubtedly

proceeds via a diol, no diol is actually isolated, as it is oxidized further, to the ortho-dione

(see section 9.2.3 (2) ). Mugdan and Young [109] also found that pertungstic acid is an efficient catalyst;

however, it is less reactive than osmium tetroxide and so was used at 60 to 70° C. In

contrast to osmium tetroxide, it is nontoxic ; also, it is cheaper. This reagent does not appear to have been applied to polycyclic, aromatic hydrocarbons.

39
Table 15. Miscellaneous oxidants used for

the oxidation of anthracene to anthraquinone"

Oxidant and conditions

Bismuth nitrate (and heating)

Cerium sulfate in 20% sulfuric acid Chromic chlorate, aqueous solution (and heating)

Ferric chlorate, aqueous solution (and heating)

Iodic acid in boiling acetic acid Iodine and concentrated nitric acid, in chloroform Manganese dioxide, in ethanol-toluene Manganese dioxide plus oxides of molybdenum or vanadium, in boiling sulfuric acid Manganese salts Potassium bromate in boiling acetic acid Potassium chlorate in concentrated formic acid Potassium chlorate plus sodium nitrate plus magnesium chloride.SHjO at 130-150° Sodium chlorate in concentrated formic acid Sodium chlorate plus magnesium chloride Sodium chlorate plus osmium tetroxide in 50% acetic acid Sodium chlorate plus vanadium pentoxide, plus 2% sulfuric acid in acetic acid Sodium chlorite plus an osmium salt, at room temperature

Sodium hypochlorite

Electrochemical oxidation in the presence of Cerium compounds

Lead dioxide, as oxygen carrier Oxygen carriers Vanadium compounds

Vanadium pentoxide in 20% sulfuric acid, at 80°

'Only references to early work are given.

References for table 15

1. L. Spiegel and H. Haymann, Ber. 59, 202 (1926).

2. Farbw. vorm. Meister Lucius and Bruening, Ger. Pat. 158,609 (1902); Chem. Zentr. 76, I, 840 (1905). A. Benrath and K. Ruland, Z. Anorg. Chem. 114, 267 (1920).

3. Farbw. vorm. Meister Lucius and Bruening, Ger. Pats. 273,318-9 (1912); Chem. Abstr. 8, 2781.

4. A. G. Williams, J. Am. Chem. Soc. 43, 1911 (1921).

5. R. L. Datta and N. R. Chatterjee, J. Am. Chem. Soc. 39, 435 (1917).

6. K. H. Meyer, Ann. 379, 37 (1911).

7. C. E. Andrews, U. S. Pat. 1,324,715 (1919); Chem. Abstr. 14, 469.

8. W. Lang, Ger. Pat. 189,178 (1902); Chem. Abstr. 2, 1209.

9. K. A. Hofmann and K. Schumpelt, Ber. 48, 816 (1915).

10. K. A. Hofmann, Ger. Pat. 277,733 (1913); Chem. Zentr. 85, II, 899 (1914). K. A. Hofmann, F. Quoos, and O. Schneider, Ber. 47, 1991 (1914).

11. K. A. Hofmann, Ber. 45, 3329 (1912).

12. H. W. Underwood, Jr., and W. L. Walsh, Org. Syn. 16, 73 (1936).

13. K. A. Hofmann and K. Ritter, Ber. 47, 2233 (1914).

14. K. A. Hofmann, Brit. Pat. 20,593 (1913); Chem. Abstr. 9, 697. K. A. Hofmann, O. Ehrhart, and 0. Schneider, Ber. 46, 1657 (1913). K. A. Hofmann and 0. Schneider, Ber. 48, 1585 (1915).

15. Farbw. vorm. Meister Lucius and Bruening, Ger. Pat 152,063 (1902); Chem. Zentr. 75, II, 71 (1904).

16. A. Fontana and F. M. Perkin, Elektrochem. Z. 11, 99 (1904).

17. C. H. Rasch and A. Lowy, Trans. Am. Electrochem. Soc. 56, 477 (1929).

18. Bayer and Co., Ger. Pat. 252,759 (1911); Chem. Abstr. 7, 455.

19. Farbw. vorm. Meister Lucius and Bruening, Ger. Pat. 172,654 (1903); Chem. Abstr. 1, 132.

20. Brit. Pat. 19,178 (1902); French Pat. 345,701 (1904); U. S. Pat. 823,435 (1906).

(2) Osmium tetroxide-pyridine. Criegee [110] discovered that osmium tetroxide is an excellent hydroxylating agent. Treatment of an olefin with an equivalent of the reagent

in cold dry ether, benzene [22] , cyclohexane [22] , or dioxane [110,111] slowly gives an

I I HC HCO.

II + OsO I ^OsO,

HC HCO

I •

addition compound, which usually is precipitated from the solution, in almost quantitative

40
yield, in less than 4 days. The product, an ester of osmic acid, may be hydrolyzed to the

cis-diol.

I I HCO^ HCOH

I ^OsO + 2 H„0 —^ I + H^OsO,

HCO^ HCOH ^

Criegee and coworkers also discovered that, if a tertiary base is added to the reaction

mixture, the initial addition of osmium tetroxide is accelerated ; pyridine is particularly

effective [22] . A bright-colored compound having the character of an osmic ester and

containing two molecules of the tertiary base per molecule is precipitated in almost quantitative yield.

I C3H3N

HCO j 0

HCO^ I ^0

C3H3N

This ester may then be hydrolyzed to the diol. Various reagents have been used for

hydrolysis, including (a) acidic solutions of potassium or sodium chlorate, (b) hydrogen

sulfide, (c) sodium sulfite in aqueous ethanol, or (d) potassium hydroxide in the presence

of L-ascorbic acid, formaldehyde, or D-mannitol ; of these, sodium sulfite and D-mannitol,

respectively, have been the most widely used. Criegee found that cis-olefins give erythrodiols, and irans-olefins give i/ireo-diols.

By use of this reagent under anhydrous conditions, with subsequent hydrolysis,

Criegee and coworkers [22] hydroxylated phenanthrene to 9,10-dihydro-9,10-phenanthrenediol. _ OH

Phenanthrene

A systematic study revealed that the reagent attacks ortho reactive centers exclusively

[5,16,112]. This behavior contrasts with the attack by a variety of other oxidants at the

most reactive jmra (or pseudo-para) centers in the molecule. The reagent is, therefore,

especially useful for determining the most reactive ortho centers in polycyclic, aromatic

hydrocarbons which also contain very reactive para or pseudo-para centers. For example,

for those hydrocarbons which contain a phenanthrene moiety having C-9 and C-10 nonfused, a quantitative estimation of the relative reactivity at the 9,10-positions of the phenanthrene moiety may be made.

On treating anthracene with the reagent, and hydrolyzing, l,2,3,4,tetrahydro-l,2,3,4-

anthratetrol is obtained. It is supposed that the initial addition is at the 1,2-bond; the

coo:

—

Anthracene

product contains a true ethylenic bond at C-3 to C-4, which readily reacts with a second

molecule of the reagent. The positions of addition for other polycyclic, aromatic hydrocarbons are given in table 3.

41
The reaction is simple and affords high yields. However, osmium tetroxide has the

following disadvantages: (1) it has a high equivalent weight, (2) it is very expensive,

(3) it is fairly volatile, and (4) its vapors are very poisonous and severely injure the eyes. (3) Oxygen. In autoxidation, oxygen can add to a very reactive bond. Thus, on

treating 1,2-dihydronaphthalene with oxygen for 430 hr at 18° C, l,2-epoxy-l,2,3,4-tetrahydronaphthalene is formed [75] , together with 3,4-dihydro-2(li/)-naphthalenone, transl,2,3,4-tetrahydro-l,2-naphthalenediol, and other products (see section 9.1.9).

OO — OQ + 00-„ + OQTM

(4) Peroxybenzoic acid. With peroxybenzoic acid, an atom of oxygen may be added

to a "double" bond to give the epoxide, as with indene [113].

1, 2 -Epoxyindan

On oxidation of dibenz [a./i] anthracene with peroxybenzoic acid [64] , an 0.04-percent

yield of the 5,6-epoxide is obtained.

Dibenz[a,,h] anthracene (6383)

5, 6-Epoxy-5, 6-dihydrodibenz anthracene

Pyrene gives the 4,5-dihydro-4,5-diol [65] , presumably via the 4, 5-epoxide, together

with other products (see sections 8.2.5 and 9.1.8).

9.2.2. Addition to, and Rupture of, a "Double" Bond

(1) Chromium trioxide. Chromium trioxide in hot acetic acid, or sodium dichromate

in aqueous sulfuric acid, can rupture a bond, presumably via the o-dione. It is likely that a cyclic addition product of the chromium trioxide at the "double" bond is first formed.

An example is the oxidation of phenanthrene to diphenic acid (see table 3).

(2) Nitric acid. Rupture of "double" bonds can be caused by nitric acid, or by nitric

acid followed by permanganate. Thus, with fuming nitric acid, triphenylene gives [114]

mellitic acid.

CO^H

42

Triphenylene (5256) Mellitic acid
(3) Organic peroxy acids. Hydrogen peroxide in acetic acid attacks the most reactive

"double" bonds of some polycyclic, aromatic hydrocarbons ; in some instances, subsequent

rupture of the "double" bond occurs (see table 3).

(4) Oxygen, catalyzed by vanadium pentoxide. Vapor-phase oxidation of chrysene

with air over vanadium pentoxide gives phthalic anhydride [97]

.

(5) Ozone.

(a) In a nonparticipating solvent. For many of the polycyclic, aromatic hydrocarbons, dissolved in an ice-cold, stable, nonparticipating solvent, one molecule of ozone adds

to a reactive "double" bond, to give an ozonide which rearranges with rupture of the bond,

possibly as follows.

0

\/

C

C —

0

/\

\/

C 0

C 0

/\

\/c—

0

/

0

\

C —0

/\

Ozonides are unstable; and so, products are isolated either by (a) reducing the

ozonide and then hydrolyzing, or (b) oxidizing further with hydrogen peroxide. The ring

fission occurs at the positions originally occupied by the most reactive bond (or bonds).

Naphthalene readily reacts with two equivalents of ozone, to give a "diozonide"

[115,116] ; slow absorption of ozone then continues until five equivalents have been taken

up. In naphthalene, the 1,2-bond has the lowest bond-localization energy [8,11]. This bond

presumably reacts first, to give a mono-ozonide which has an olefinic 3,4-bond that is rapidly attacked. Treatment of this product with water gives phthalaldehyde. The reaction was originally considered to proceed as follows,

0. 0.

0,

0. C=0

H

Phthalaldehyde

via the 1,2 :3,4-diozonide. However, according to Bailey [116], the reaction does not in- volve formation of a diozonide, but of a polymer of the intermediate ion I.

Nevertheless, for approximate depictions, the attack of ozone is more conveniently shown

as ^Os. The absorption of five equivalents of ozone was originally explained as involving

43
formation of the penta-ozonide from the diozonide (A or B).

For naphthalene and phenanthrene, the attack of ozone can be explained as attack

at the bond of lowest bond-localization energy or at the centers of lowest atom-localization

energy. Ozone reacts with phenanthrene at the 9,10-bond exclusively and one equivalent of ozone is absorbed. The product was originally considered to be the monomeric ozonide I, but later work [117,118] has shown that it is a polymer of II.

1 n

Ozonolysis of a number of nonlinear, polycyclic hydrocarbons in inert solvents has

been studied [73]. Criegee and coworkers [119] had suggested that, under these conditions, intermediate ions are formed and that these interact to give polymeric ozonides.

Wibaut and deBoer [120] ozonized phenanthrene and isolated a trimer. Bailey and Mainthia [121] decided that a mixture of polymers is formed; and Copeland and coworkers

[73] confirmed this conclusion.

Triphenylene is attacked [73] at the 1,2-bond.

In picene, the 5,6- and 7,8-bonds have the lowest bond-localization energies. Picene

readily absorbs two equivalents of ozone; on oxidative decomposition of the product, a

44
35 percent yield of an anhydride is obtained [73]

,

8 ^ Co^h

Picene (6384)

Similarly benzo[g']chrysene is attacked at the 9,10-bond [73].

Benzo[_g]chrysene (6385) (69%)

Dibenzo [c,fif] phenanthrene is attacked at the 1,2- and 5,6-bonds [73].

03

Dibenzo[£,^] phenanthrene (6387) (657o)

Other examples of attack by ozone at the bond (or bonds) of lowest bond-localization

energy are given in table 3. Examples involving attack by ozone at para or pseudo-para reactive centers, instead

of (or as well as) at ortho reactive centers, are discussed in section 9.1.13. (b) In a participating solvent. If ozonolysis is conducted in the presence of a participating solvent, such as methanol, the solvent combines with the ozonolysis product

[116]. For example, ozonolysis of naphthalene in methanol gives 4-methoxy-2,3-benzodioxan-l-ol [122], which, on refluxing in methanol, gives methyl phthalaldehydate.

2 0,

2 MeOH

c-o

c-C

h

OH

OCHL

OCH.

I ' HOO-CH

I 0=CH

45
(6) Potassium permanganate. As discussed later (section 9.2.3 (6) ), potassium permanganate probably gives a cyclic, manganate ester at the most reactive bond ; in water,

this presumed ester hydrolyzes immediately to the glycol. With some polycyclic, aromatic

hydrocarbons, this glycol is now oxidized by the permanganate, with oxidative cleavage

of the C-C bond of the glycol, affording aldehyde groups which are, in turn, oxidized to carboxyl groups.

The effect may differ, according as the solution is acid or alkaline. Thus, in alkaline

solution, naphthalene is oxidized by permanganate to phthalonic acid [123,124], but in

acid solution, the oxidation proceeds a stage further, giving phthalic acid [124]. Simi0

Phthalonic acid Phthalic acid

larly, triphenylene is oxidized [114b] to mellitic acid.

9.2.3. Oxidation of or//to-Methine Groupings

(1) Chromium trioxide. Chromium trioxide in glacial acetic acid, or sodium dichromate in sulfuric acid, may oxidize two adjacent methine groupings to the corresponding or^/io-dione (see table 3). It has been suggested that a chromate ester is formed as the intermediate, as with ester formation by osmium tetroxide.

Oxidation of picene gives a mixture [125] of the 5,6-dione and the 13,14-dione, in the

ratio of 3.6 to 1.

Picene (6384) 5 , 6 -Picenedione 13 , 14 -Picenedione

Similarly, benzo[gf]chrysene gives the 9,10-dione [126].

10

Benzo[^]chrysene (6385)

(2) Hydrogen peroxide, catalyzed by osmium tetroxide. The o-dione maybe obtained

by oxidation of two adjacent methine groups with hydrogen peroxide catalyzed by osmium

tetroxide. The bond that, from calculations of bond order and localization energy, is the

most reactive is the one attacked (see table 3).

Cook and Schoental [65a] stated that, on oxidation of pyrene with this reagent in

tert-hutyl alcohol, a mixture of 1,6-pyrenedione and 1,8-pyrenedione was formed. How46
ever, using the same reagent in acetone, Oberender and Dixon [127] obtained 4,5-pyrenedione. The 4,5-bond has the lowest bond-localization energy, and the 1,6- and 1,8-diones were not detected.

(3) Iodic acid. Iodic acid in glacial acetic acid, at the boiling point, oxidizes phenanthrene to phenanthrenequinone [128].

(4) Osmium tetroxide and sodium periodate. With this reagent, pyrene is oxidized

exclusively at the 4,5-bond, giving [127] a 23 percent yield of 4,5-pyrenedione and a 24

percent yield of the lactol of 5-formyl-4-phenanthrenecarboxylic acid. Presumably, the as0 = C ^cmqH

mium tetroxide reacts first, to give the 4,5-diol, and this is then oxidized to the 4,5-dione

by the periodate.

4, 5 -Dihydro-4 , 5 -pyr enediol

(5) Peroxyacetic acid. This reagent may attack a reactive double bond, as for

naphthalene, phenanthrene, benz [a] anthracene, and chrysene (see table 3).

(6) Potassium permanganate. Potassium permanganate is capable of hydroxylating

a double bond to give a glycol, isolation of which is difficult or impossible because the glycol itself is then subject to oxidation. However, where the glycol has been isolated and cis- or iraws-diols could be formed (e.g., from cyclohexene), the product is exclusively the

cis-{erythro) -diol, indicating that the addition involves formation of the cyclic, manganate ester. \/

C

/\

0 o —p Mn

0 OK

HCO \ /

Mn

(H^O)

/ \ e ^

HCO 0 K

HCOH

HCOH

+ MnO^ + KOH

With some hydrocarbons, oxidation then proceeds, to give the o-dione. Thus, phenanthrene gives [73,129] a 51 percent yield of phenanthrenequinone, together vdth less than 5 percent of diphenic acid.

47
Similarly, chrysene gives the 5,6-dione [73].

5, 6-Chrysenedione

(7) Ruthenium dioxide and sodium periodate. This reagent reacts with pyrene [127]

at the 4,5-bond and also at the carbon atoms of greatest electron density, giving 11 percent of 4,5-pyrenedione, 2 percent of 1,6-pyrenedione, and 1 percent of the lactol of

4-formyl-5-phenanthrenecarboxylic acid, together with 10 percent of an unidentified

aldehyde.

(8) Selenium dioxide. In the absence of a solvent, selenium dioxide has practically no action on phenanthrene ; a 3 percent yield of the quinone is obtained [55a]. In sus- pension in water or dissolved in nitrobenzene, no quinone is formed [107a,b].

0 0

Phenanthr enequinone

10. Oxidative Degradation of an Alkyl Side-Chain

For polycyclic, aromatic hydrocarbons bearing an alphatic side-chain, some oxidants

oxidize the side chain more readily than they attack the nucleus.

10.1. Chromium Tnoxide

Used below 40° C, chromium trioxide (or chromic acid) in acetic anhydride oxidizes a methyl group to an aldehyde group.

CrO„ CrO„

aryl—CH^ ^—> aryl—CHCOAc)^

^ aryl—CHO

Hot chromium trioxide in acetic acid (or chromic acid in aqueous sulfuric acid) oxidizes an alkyl side-chain to a carboxyl group.

CrO

aryl— (CH2)^—CH^

^ aryl—CO2H

10.2. Nitric Acid

For use as an oxidant, the nitric acid should be diluted; conditions for nitration

should be avoided. A methyl group is then oxidized to a carboxyl group.

HNO3

aryl—CH > aryl—CO2H

48
10.3. Potassium Permanganate

An excess of potassium permanganate, in acid or alkali, oxidizes an alkyl side-chain

to a carboxyl group.

aryl— (CH2)^~CH2 ^ > aryl—CO^'H

KMnO^

11. Summary of Action of Various Oxidants

The various kinds of oxidation may be grouped in four main categories, according to the type of reaction involved. These are (1) one-center attack, (2) addition to a double

bond, (3) addition at para centers, (4) formation of o-, pseudo-p-, or p-diones. Table 16

summarizes the kinds of action of the various oxidants under these four categories.

Table 16. Action of various oxidants

Oxidant

Benzoyl peroxide

Chromium trioxide (or sodium dichromate)

Hydrogen peroxide plus osmium tetroxide

Iodic acid Lead tetraacetate

Nitric acid, nitrates, nitrites Nitrogen oxides Osmium tetroxide plus pyridine (and hydrolysis)

Osmium tetroxide plus sodium periodate

Oxygen

Oxygen plus ultraviolet light

Oxygen plus vanadium pentoxide

Oxygen plus various catalysts Ozone (with subsequent treatment)

Peroxyacetic acid Peroxybenzoic acid Potassium chlorate plus osmium tetroxide Potassium permanganate

Ruthenium dioxide plus sodium periodate

Selenium dioxide

Kind of action

»

1,4

1,2,4

1,2,4

4

1,3

2,3,4

3,4

2

4 1,2,3,4

1,3

2,4

4 1,2,3,4

2,4 , 1,242,4

4

1,4

'Key: 1, one-center attack; 2, addition to a double bond; 3, addition at para centers; 4, formation

of 0-, pseudo-p-, or p-dione.

12. References

[1] A. M. Patterson, L. T. Capell, and D. F. Walker, The Ring Index, 2d ed. (Am. Chem. Soc, 1960).

[2] E. Sawicki, Chemist-Analyst 53 (No. 1), 24 (1964).

[3] H. L. Falk, P. Kotin, and A. Miller, Intern. J. Air Pollution 2, 201 (1960); H. L. Falk, Natl. Cancer

Inst. Mono. 9, 255 (1962).

[4] J. Maisin and A. de Jonghe, Compt. Rend. Soc. Biol. 117, 111 (1934).

[5] J. W. Cook and R. Schoental, Nature 161, 237 (1948).

[6] J. Fritzsche, J. Prakt. Chem. [1] 106, 274 (1869).

[7] B. Pullman and A. Pullman, Progr. Org. Chem. 4, 31 (1958).

[8] M. J. S. Dewar, J. Am. Chem. Soc. 74, 3357 (1952).

[9] E. Clar, Aromatische Kohlenwasserstoffe, Springer-Verlag, Berlin, 1952. [10] R. D. Brown, J. Chem. Soc. 1950, 691. [11] R. D. Brown, J. Chem. Soc. 1950, 3249. [12] R. D. Brown, Australian J. Sci. Res. A2, 564 (1949).

[13] G. M. Badger, J. Chem. Soc. 1949, 456. [14] G. M. Badger, J. Proc. Roy. Australian Chem. Inst. 17, 14 (1950).

[15] G. M. Badger and R. I. Reed, Nature 161, 238 (1948).

[16] J. W. Cook and R. Schoental, J. Chem. Soc. 1948, 170.

49
[17] M. S. Newman, J. Am. Chem. Soc. 62, 2295 (1940) ; M. S. Newman and W. B. Wheatley, J. Am. Chem.

Soc. 70, 1913 (1948); M. Szwarc and F. Leavitt, J. Am. Chem. Soc. 78, 3590 (1956).

[18] A. O. Mcintosh, J. M. Robertson, and V. Vand, J. Chem. Soc. 1954, 1661. [19] A. Pullman and B. Pullman, Cancerisation par les substances chimiques et structure moleculaire

(Masson, Paris, 1955).

[20] A. Pullman and B. Pullman, Rev. Sci. 84, 145 (1946); A. Pullman, Ann. Chim. [12] 2, 5 (1947); R. Daudel, Bull. Assoc. Franc. Etude Cancer. 35, 110 (1948).

[21] C. F. Cross, E. J. Bevan, and T. Heiberg, Ber. 33, 2015 (1900); H. Gelissen and P. H. Hermans, Ber.

58, 476 (1925); A Perret and R. Perrot, Helv. Chim. Acta 28, 558 (1945); G. Stein and J. Weiss,

Nature 161, 650 (1948); G. Stein and J. Weiss, J. Chem. Soc. 1949, 3245. [22] R. Criegee, B. Marchand, and H. Wannowius, Ann. 550, 99 (1942).

[23] B. Pullman and A. Pullman, Les theories electroniques de la chimie organique (Masson, Paris,

1952, p. 583).

[24] A. Zinke and E. Unterkreuter, Monatsh. 40, 405 (1919).

[25] A. L. Sklar, J. Chem. Phys. 5, 669 (1937).

[26] G. N. Lewis and M. Kasha, J. Am. Chem. Soc. 67, 994 (1945); A. C. Pitts, J. Chem. Phys. 18, 1416

(1950).

[27] D. F. Evans, Nature 178, 534 (1956); J. Chem. Soc. 1957, 1351.

[28] D. F. Evans, J. Chem. Soc. 1957, 3885; 1959, 2753; Proc. Roy. Soc. (London) A255, 55 (1960).

[29] H. Tsubomura and R. S. Mulliken, J. Am. Chem. Soc, 82, 5966 (1960); H. Kuroda, J. Chem. Phys.

33, 1586 (1960); J. Jortner and U. Sokolov, J. Phys. Chem. 65, 1633 (1961); E. C. Lim and V. L. Kowalski, J. Chem. Phys. 36, 1729 (1962); H. Tsubomura and R. P. Lang, J. Chem. Phys. 36, 2155 (1962).

[30] D. F. Evans, J. Chem. Soc. 1961, 1987.

[31] E. J. Bowen and A. Norton, Trans. Faraday Soc. 35, 44 (1939); J. A. Miller and C. A. Baumann,

J. Am. Chem. Soc. 65, 1540 (1943); B. Stevens, Trans. Faraday Soc. 51, 610 (1955) ; E. J. Bowen

and J. Sahu, J. Phys. Chem. 63, 4 (1959); G. Jackson, R. Livingston, and A. C. Pugh, Trans. Fara- day Soc. 56, 1635 (1960); L. E. Lyons and J. W. White, J. Chem. Soc. 1960, 5213; W. R. Ware,

J. Phys. Chem. 66, 455 (1962); A. Heller, J. Chem. Phys. 36, 2858 (1962).

[32] H. Weil-Malherbe and J. Weiss, Nature 149, 471 (1942).

[33] I. B. Berlman and A. Weinreb, Mol. Phys. 5, 313 (1962).

[34] J. Weiss, Nature 145, 744 (1940).

[35] J. Weiss, Nature 147, 512 (1941).

[36] V. Gold and F. L. Tye, J. Chem. Soc. 1952, 2172, 2181, 2184.

[37] Y. Yokozawa and L Miyashita, J. Chem. Phys. 25, 796 (1956).

[38] (a) S. I. Weissman, E. de Boer, and J. J. Conradi, J. Chem. Phys. 26, 963 (1957); (b) W. K. Hall,

J. Catalysis 1, 53 (1962); (c) D. N. Stamires and J. Turkevich, J. Am. Chem. Soc. 86, 749 (1964).

[39] G. Dallinga, E. L. Mackor, and A. A. V. Stuart, Mol. Phys. 1, 123 (1958).

[40] A. Carrington, F. Dravnieks, and M. C. R. Symons, J. Chem. Soc. 1959, 947. [41] W. L Aalbersberg, G. J. Hoijtink, E. L. Mackor, and W. P. Weijland, J. Chem. Soc. 1959, 3049. [42] W. I. Aalbersberg, J. Gaaf, and E. L. Mackor, J. Chem. Soc. 1961, 905. [43] Y. Matsunaga, Bull. Chem. Soc. Japan 34, 1293 (1961).

[44] J. Fritzsche, Compt. Rend., 64, 1035 (1867); J. Prakt. Chem. 101, 333 (1867).

[45] R. Luther and F. Weigert, Z. Physik. Chem. 51, 297 (1905); 53, 385 (1905).

[46] W. R. OrndorflF and F. K. Cameron, Am. Chem. J. 17, 658 (1895) ; J. Hengstenberg and J. Palacios,

Anales Soc. Espan. Fis. Quim. 30, 5 (1932); F. D. Greene, S. L. Misrock, and J. R. Wolfe, Jr., J. Am. Chem. Soc. 77, 3852 (1955).

[47] C. Dufraisse and M. Gerard, Bull. Soc. Chim. France [5] 4, 2052 (1937).

[48] M. Suzuki, Bull. Chem. Soc. Japan 18, 146 (1943); 22, 172 (1949); 23, 120 (1950).

[49] S. S. Bhatnagar, P. L. Kapur, and G. Kaur, Proc. Indian Acad. Sci. lOA, 468 (1939).

[50] B. Stevens, Nature 192, 725 (1961).

[51] G. W. K. Cavill, A. Robertson, and W. B. Whalley, J. Chem. Soc. 1949, 1567. [52] Y. Sprinzak, J. Am. Chem. Soc. 80, 5449 (1958).

[53] H. Hock and F. Depke, Chem. Ber. 83, 327 (1950).

[54] H. Hock, S. Lang, and G. Knauel, Chem. Ber. 83, 227 (1950).

[55] (a) J. J. Postowsky and B. P. Lugowkin, Ber. 68, 852 (1935); (b) G. M. Badger, J. Chem. Soc. 1941,

535. [56] L. Monti, Gazz. Chim. Ital. 68, 608 (1938).

[57] L. Monti, Atti Congr. Intern. Chim. 3, 256 (1939); Chem. Abstr. 33, 9316 (1939).

[58] D. L Davies, D. H. Hey, and G. H. Williams, J. Chem. Soc. 1958, 1878. [59] D. H. Hey, J. Chem. Soc. 1934, 1966.

[60] K. H. Meyer, Ann. 379, 37 (1911).

50
[61] L. F. Fieser and E. B. Hershberg, J. Am. Chem. Soc. 60, 1893, 2542 (1938); L. F. Fieser and S. T. Putnam, J. Am. Chem. Soc. 69, 1038, 1041 (1947).

[62] K. E. Schulze, Ber. 18, 3036 (1885).

[63] W. Treibs and J. Thoermer, Chem. Ber. 94, 1925 (1961).

[64] B. L. Van Duuren, I. Bekersky, and M. Lefar, J. Org. Chem. 29, 686 (1964).

[65] E. Boyland and P. Sims, Biochem. J. 90, 391 (1964).

[65a] J. W. Cook and R. Schoental, J. Chem. Soc. 1950, 47. [66] J. Meisenheimer, Ann. 323, 205 (1902); 355, 249 (1907); J. Meisenheimer and E. Connerade, 330, 133 (1904); R. Oda, J. Soc. Chem. Ind. Japan 42, Suppl. 414 (1939).

[67] A. Laurent, Ann. Chim. Phys. [2] 60, 220 (1835); 66, 136 (1837); Ann. 34, 293 (1840).

[68] O. Dimroth, Ber. 34, 219 (1901); R. Scholl and J. Mansfeld, Ber. 43, 1734 (1910).

[69] W. Kemula and A. Grabowska, Bull. Acad. Polon. Sci. 6, 747 (1958); 8, 517, 525 (1960).

[70] W. F. O'Connor and E. J. Moriconi, Ind. Eng. Chem. 45, 277 (1953).

[71] R. T. Arnold and R. Larson, J. Org. Chem. 5, 250 (1940).

[72] L M. Roitt and W. A. Waters, J. Chem. Soc. 1949, 3060.

[73] P. G. Copeland, R. E. Dean, and D. McNeil, J. Chem Soc. 1961, 1232. [74] H. Schrader, Ges. Abhand. Kenntn. Kohle 4, 310 (1920); Chem. Abstr. 15, 2850 (1921).

[75] H. Hock and F. Depke, Chem. Ber. 83, 317 (1950).

[76] H. Hock and S. Lang, Ber. 77, 257 (1944) ; H. Hock and F. Depke, Chem. Ber. 84, 122 (1951).

[77] G. A. Russell, J. Am. Chem. Soc. 78, 1035 (1956).

[78] C. Dufraisse and M. Gerard, Compt, Rend. 201, 428 (1935).

[79] E. Clar and F. John, Ber. 63, 2967 (1930).

[80] J. W; Cook and R. H. Martin, J. Chem. Soc. 1940, 1125. [81] C. Dufraisse and R. Horclois, Bull. Soc. Chim. France [5] 3, 1880 (1936).

[82] E. Clar, Ber. 72, 1817 (1939).

[83] C. Dufraisse and J. Mathieu, Bull. Soc. Chim. France 1947, 307. [84] C. Moureu, C. Dufraisse, and P. M. Dean, Compt. Rend. 182, 1440, 1584 (1926). C. Moureu, C. Dufraisse, and L. Girard, Compt. Rend. 186,1027 (1928).

[85] C. Dufraisse and J. L. Bras, Bull. Soc. Chim. France [5] 4, 349 (1937); C. Dufraisse, ibid. [5] 6, 422

(1939). M. T. Mellier, Compt. Rend. 219, 188 (1944).

[86] H. H. Perkampus, Naturwissenschaften 44, 614 (1957).

[87] H. H. Perkampus, Z. Elektrochem. 62, 1152 (1958).

[88] Y. Matsumoto and E. Funakubo, Nippon Kagaku Zasshi 72, 731 (1951); T. Nagai and E. Funakubo,

Kogyo Kagaku Zasshi 64, 1053 (1961).

[89] Y. Matsumoto, Nippon Kagaku Zasshi 72, 733 (1951).

[90] D. P. Craig and P. C. Hobbins, J. Chem. Soc. 1955, 2309.

[91] G. Kortiim, Angew. Chem. 71, 461 (1959). E. Voyatzakis, D. Jannakoudakis, T. Dorfmiiller, and C. Sipitanos, Compt. Rend. 249, 1756 (1959); 250, 112 (1960). E. Voyatzakis, D. Jannakoudakis, T. Dorfmiiller, C. Sipitanos, and G. Stalidis, Compt. Rend. 251, 2696 (1960).

[92] G. Kortum and W. Braun, Ann. 632, 104 (1960).

[93] R. M. Roberts, C. Barter, and H. Stone, J. Phys. Chem. 63, 2077 (1959).

[94] J. K. Fogo, J. Phys. Chem. 65, 1919 (1961). R. L. Hodgson and J. F. Raley, Abstr. Papers Am.

Chem. Soc. Meeting 147, 29H (1964).

[95] J. J. Rooney and R. C. Pink, Proc. Chem. Soc. 1961, 70. J. A. N. Scott, B. D. Flockhart, and R- C. Pink, Proc. Chem. Soc. 1964, 139. [96] H. W. Kohn, J. Phys. Chem. 66, 1185 (1962).

[97] M. V. Goftman and A. I. Golub, Zh. Prikl. Khim. 29, 1256 (1956).

[98] C. E. Senseman and 0. A. Nelson, Ind. Eng. Chem. 15, 521 ( 1923).

[99] E. F. Pratt and L. E. Trapasso, J. Am. Chem. Soc. 82, 6405 (1960).

[100] E. G. E. Hawkins, J. Chem. Soc. 1957, 3858. P. S. Bailey and J. B. Ashton, J. Org. Chem. 22, 98

(1957).

[101] P. G. Copeland, R. E. Dean, and D. McNeil, Chem. Ind. (London) 1959, 329. [102] E. J. Moriconi, W. F. O'Connor, and L. B. Taranko, Arch. Biochem. Biophys. 83, 283 (1959). P. G. Copeland, R. E. Dean, and D. McNeil, J. Chem. Soc. 1961, 3858. [103] E. J. Moriconi, W. F. O'Connor, and F. T. Wallenberger, J. Am. Chem. Soc. 81, 6466 (1959).

[104] P. G. Copeland, R. E. Dean, and D. McNeil, Chem. Ind. (London) 1960, 98. [105] F. T. Wallenberger, Tetrahedron Letters 1959, No. 9, 5. [106] E. J. Moriconi, B. Rakoczy, and W. F. O'Connor, J. Am. Chem. Soc. 83, 4618 (1961).

[107] (a) S. Astin, L. deV. Moulds, and H. L. Riley, J. Chem. Soc. 1935, 901; (b) compare, G. M. Badger,

J. Chem. Soc. 1947, 764. [108] N. A. Milas, J. Am. Chem. Soc. 59, 2342 (1937); N. A. Milas and S. Sussman, J. Am. Chem. Soc.

58, 1302 (1936); 59, 2345 (1937).

[109] M. Mugdan and D. P. Young, J. Chem. Soc. 1949, 2988.

51
[110] R. Criegee, Ann. 522, 75 (1936).

[Ill] D. H. R. Barton and D. Elad, J. Chem. Soc. 1956, 2085. [112] J. W. Cook, J. Chem. Soc. 1950, 1210. [113] M. Mousseron and R. Richaud, Bull. Soc. Chim. France, 1946, 629. W. Hiickel and F. J. Bollig, Chem.

Ber. 86, 1137 (1953).

[114] (a) C. Mannich, Ber 40, 159 (1907); (b) B. Juettner, J. Am. Chem. Soc. 59, 1472 (1937).

[115] C. Harries, Ann. 343, 311 (1905). L. Seekles, Rec. Trav. Chim. 42, 706 (1923). J. P. Wibaut and L. W. F. Kampschmidt, Koninkl. Ned. Akad. Wetenschap. Proc. 53, 1109 (1950). L. W. F. Kampschmidt and J. P. Wibaut, Rec. Trav. Chim. 73, 431 (1954).

[116] P. S. Bailey and F. J. Garcia-Sharp, J. Org. Chem. 22, 1008 (1957).

[117] J. P. Wibaut and T. J. de Boer, Koninkl. Ned. Akad. Wetenschap. Proc. B59, 421 (1956).

[118] P. S. Bailey and S. B. Mainthia, J. Org. Chem. 21, 1335 (1956).

[119] R. Criegee and G. Wenner, Ann. 564, 9 (1949). R. Criegee, Ann. 583, 1 (1953). R. Criegee, G. Blust,

and H. Zinke, Chem. Ber. 87, 766 (1954). R. Criegee, A. Kerckow, and H. Zinke, Chem. Ber.

88, 1878 (1955).

[120] J. P. Wibaut and T. J. de Boer, Rec. Trav. Chim. 78, 183 (1959).

[121] P. S. Bailey and S. B. Mainthia, J. Org. Chem. 23, 1089 (1958).

[122] P. S. Bailey, S. S. Bath, F. Dobinson, F. J. Garcia-Sharp, and C. D. Johnson, J. Org. Chem. 29, 697

(1964).

[123] J. Tcherniak, German Pats. 79,693 (1895), 86,914 (1896). C. Graebe and F. Trumpy, Ber. 31, 369

(1898). R. C. Fuson, J. Am. Chem. Soc. 48, 1093 (1926).

[124] J. Tcherniak, J. Chem. Soc. 109, 1236 (1916).

[125] W. Davies and B. C. Ennis, J. Chem. Soc. 1959, 915. [126] C. L. Hewett, J. Chem. Soc. 1938, 193. [127] F. G. Oberender and J. A. Dixon, J. Org. Chem. 24, 1226 (1959).

[128] A. G. Williams, J. Am. Chem. Soc. 43, 1911 (1921).

[129] G. Charrier and A. Beretta, Gazz. Chim. Ital. 54, 765 (1924). W. A. Bone, L. G. B. Parsons, R. H.

Sapiro, and C. M. Groocock, Proc. Roy. Soc. London A148, 492 (1935). R. B. Randall, M. Benger,

and C. M. Groocock, Proc. Roy. Soc. London A165, 432 (1938).

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