Chemical Structure of Kitol (I)Double Bonds and Hydroxyl Groups

BYYOSHIMORI 0MOTE

In 1943 Embree and Shantz 1) postulated the molecular formula
C40H 58(0H) 2 for kitol isolated from whale liver oil, and in 1947 Baxterand co-workers 2) succeeded to obtain kitol in crystalline form, but sincethat time no research about the chemical structure of kitol has beenreported. The author 3) studied on thermal decomposition of kitol withabsorption spectra, yet definite conclusion has not been obtained. The
decomposition of kitol has smoothly occurred only in case of moleculardistillation, different from the pyrolyses of common substances. This
interest reaction must be connected with the chemical structure ofkitol, so that the author planned to confirm its structure and the study
is now going on. This paper is concerned with results from preparatory experiments on double bonds, especially conjugated double bonds,and hydroxyl groups in kitol molecule.
Hydrogenation of Kitol Concentrate.-Through the hydrogenationof kitol concentrate having E (286 mµ) of 580, Embree and Shantz
determined eight double bonds in a molecule. The author tried topurify kitol with themethod similar to that oftheir report, obtaining
the concentrate having
E (290 mµ) of 482, which
was used in the study totrace the hydrogenerat:!.on curve, while thenumber of double bonds
was not confirmed. As
20 4o
60 so 100 120 140 160 iso 200 220 2;0shown in Fig. 1, it wasTime, minutes.
remarkable that hydroFig. 1. Hydrogenation _curve of kitol. .
gen absorption proceeded
P : end point of the reduction of platirapidly during the former
num oxide catalyst.
two third period, butvery slowly during the remaining one third period.
Conjugated Double Bonds.-The absorption maximum of kitol wasreported 290 mµ (no s~lvent being mentioned) by Baxter etc. 2), 286 mµ194

Y: 0MOTE(in ethanol) by Embree etc. 1), while the author obtained 290 mµ (inisopropanol) in previous paper 3), and 284 mµ (in isopropanol) in thisreport. These differences seem to be due to steric isomerization ofkitol, besides to its change during purification.
From the absorption spectrum, Barua and Morton 5) proposed four
conjugated double bonds in kitol,C.46 ----_,......-_,..---.---i
considering five ones in vitamin A.
The author has independently had
0.44
the same opinion as theirs for thelast two years. The data of0.42
absorption spectra about hydro7carbons6) and alcohols ) with a
0.40
conjugated system shows that theaddition of each new -CH=0.38
CH- group causes the absorption
bands to shift toward the longer(3')-(2')
0.36
wave length region by some 40 >.
C)mµ in the region of 250 mµ to i:::~350mµ.

.0::...
00.34

Therefore, kitol having an 2absorption maximum at 285-290 < 0.32mµ must have one less conjugated0.30
double bonds, which furthermore(3)-(2)
situated in the chain bond, not
0.28
in the ring one, than vitamin A
having a maximum at 3250.26
8 mµ.
It was, moreover, proved
0.24
through absorption spectra that290
280300conjugated double bond in kitol
Wave length, mµ.
reacted with maleic anhydride toFig. 2. Reaction of kitol with maleic
decrease its extinction as shown
anhydride, spectrophotometric curve of :in Fig. 2. As clarified in the (1)kitol, (1') kitol after heating, (3)-(2)figure about 30% of kitol reacted kitol immediately after mixing withanhydride, and (3')-(2') kitol afterwith maleic anhydride in toluene maleic
heating with maleic anhydride solution.
at 100° for thirty minutes.
Position of Hydroxyl Groups in Perhydrokitol.-Hydrogenated kitol,which will be called "perhydrokitol" was obtained as white solid
through hydrogenation of kitol. The carbon hydrogen analyses ofperhydrokitol concentrate about agreed with the formula C4oH7602 , thisChemical Structure of Kitol (I)sample being used in the following experiments. Though kitol itself
is unstable, perhydrokitol, being a saturated compound, seemed to bestable. As the position of hydroxyl groups in perhydrokitol is sameas that of groups in kitol, one can clarify the position of hydroxyl·groups in kitol based on the experiments with perhydrokitol.
From this standpoint perhydrokitol was examined by Murahashi'smethods) and was proved to be primary alcohol: 44-69% of thehydroxyl group in perhydrokitol were esterified after heating at 155°
· for one hour with phenylacetic acid, under the same conditions 3959% in case of cetyl alcohol (primary), and in case of cholesterol (ringand secondary) 16-34%.
In order to ascertain the fact the esterification rate with phthalicanhydride was measured. The percentage of esterified hydroxyl group
after heating for one hour to that after heating for thirty hours wasobserved with perhydrokitol, cetyl alcohol.and cholesterol, 25.4%, 29.5%
and 0.0% being respectively obtained, so that perhydrokitol was proved
to be primary alcohol. Thus, the hydroxyl groups in perhydrokitol,
accordingly in kitol, was found to be primary, just same as that ofvitamin A, from which the author may presume that two moles ofvitamin A polymerize into kitol without any change in the position ofhydroxyl groups.

Experimental Part
1. Kitol Concentrate.-The unsaponifiable matter from Antarctic whale liver oil
was distilled in a molecular still to distil out vitamin A, the remaining portion4) was
chromatographed four times on alumina in petroleum ether to. produce kitol concentrate, which was yellowish white solid having an absorption maximum at 284 mµ,E (284 mµ) of 489 and E (290 mµ) of 482. Compared with a crystalline kitol having
E (290 mµ) of 707, the concentrate contained only 68% of pure kitol, yet appeared to
be chromatographically pure. It melted at 87-90°, giving bloodish red color with
antimony triohloride reagent, deep red with trichloracetic acid, and red then yellow
with concentrated sulfuric acid and acetic anhydride reagent.
2. Hydrogenation of Kitol.-1.0387 g. of above concentrate was dissolved in 20 cc.
glacial acetic acid, being hydrogenated with 0.500g. of platinutn oxide catalyst toproduce the hydrogenation curves shown in Fig. 1. The total volume of absorbedhydrogen was 277 cc., so the 271 cc. (at normal state) of hydrogen for one gratn of thesample. Assuming the molecular formula C40H 600 2 and· eight double bonds one gramof kitol must consume 313 cc. of hydrogen, then the fouud volume absorbed corresponds
87% of the calculated volume.
3, Reaction of Kitol with Maleic Anhydride.-Threa s::tmples were prepared : (A)kitol solution (80 mg. kitol per 100 cc. toluene), (B) tn'l.leic anhydride solution (5 g.
maleic anhydride per 100 cc. toluene), and (C) an equivolume mixture of (A) and (B).
(A), (B) and (C) were heated for thirty minutes at 100°. Before and after he.ating,Y. 0MOTE

196

exactly 1 cc. of the sample solutiou was pipetted, diluted with isopropanol into 50 cc.,with wblch thi;i absorption spectrum wa'! measured. Correcting the absorption byt<qJqene, a!),d adjusting the dilution same, the absorbancy of e:i.ch sample was caland aummarized.
in Table·''''.

culatedI.

TableI.

Re~ction of Kitol with Maleic Anhydridem,.

(2)'
(1)'
(3)'
(2)
(3)
(1)
0.410
0.270
0.576
0.640
0.27150.4325
0.412
0.237
0.549
0.615
0.231
0.4.40
28'!
0.394
0.191
290
0.55650.48950.423
0.17330.339
0.138
0.3965300
0.4-055
0.361
0.1113
Absorbancy with same dilution. of (1) kitol solution (A), (2) maleic
anhydride solution (B), and (3) equivolume mixture (C): and of (1)', (2)'and (3)', corresponding to (1), (2) and (3) after heating for thirty minutes
at 100°.
280

fro111 Table I, (3)-(2) represents the absorption only by kitol immediately after
mixing with maleic anhydride in the solvent, while (3)'-(2)' means that of kitol after
he11.ting in maleic anhydride solution. These values are plotted in Fig. 2, (above shown).
4~ Ferbydrokitol.-:The colorless transparent solution of hydrogenated kitol wasfilte:rsid to separate from catalyst, added with excess volume of water, and extractedwith ether. Ether solution was evaporated, the re3idue being saponified with methanolic
potash. The nonsaponifiable matter was extracted with ether. After evaporating
ether in vacuo the remaining portion became white solid which could not easily ba
crystallized. The elementary analyses of the compound were as follows :FoundcH
0 (diff.)

(1)
81.11
12.50
6.40

(2)
80.78
12.75
6.47

Required for
C40H1602
81.54
13.02
5.44

Molecular weight was determined by cryoscopic (camphor) method:
Sample,mg.
10.02
5.48

Camphor,mg.
121.17104.32Temperature
difference
9.3
4.5
Required for C40H7002

Molecularweight355
469
589

S. Determination of Hydroxyl Group i11 Perhydrokitol.-Customary methods 9J lOJ
to determine OH groups were semimicronized as follows.

Reagent: 2g. of phthalic anhydride (sublimed) to 12cc. pyridine. Standard aqueoussolution, 0.01026n (to benzoic acid).
Method: A w<iighed sample in a small thin glass test-tube is added with exact volum3(0.210 cc.) of the raag<int. Sealing the test-tuba, it is kept at 100° for seventy-fiva.minutes. Aftev the reaction the sealed tub3 was broken in the flas~, lee, wa.terp~tassium hydroxiderI

Chemical Structure of Kitoi (f}19'7added, then a few drops of phenolphthalein indicator dropped into, and the flask contents
are titrated with standard alkali solution. A blank is run in the same manner as thesample, and the difference of alkali cc. used for the sample and tha1; for a blankshows the alkali cc. corresponding to the hydroxyl group.
The data with perhydrokitol, cetyl alcohol and cholesterol are summarized in thefollowing. In the table, corr. OH% means found OH% minus quantity of free acid in·the sample, expressed in OH%. Free acids in perhydaokitol, cetyl alcohol and choie-·
sterol were respectively found to ~e 0.13, 0.09 and 0.42 OH%.-

Per hydrokitol

Sample,
mg.
22.48
13.30

Alkali,
cc.
11.60
7.82

8.99
10.25

8.86
10.12

5.76
5.76

Cetyl
alcohol

19.98
12.91

12.30
9.80

10.72
13.23

10.6
13.1

6.95
6.95

Cho lesterol

29.90
4..49
7.70
6.15
23.51
8.30
OH%= (0.01026x17.0xcc./mg.)x100%

4.07
5.73

4.40
4.40

OH%

corr. OH% theor. OH%

6. Rate of Esterification of Perhydrokitol with Phenylacetic Acid. - Murahashi'smethod B) was used, except that 10 cc. met~anol plus 1 cc. chloroform were added before
titration in order to dissolve the solid which was insoluble in aqueous alkali solution.
A blank, of course, was carried witk the solvent. Data with cetyl alcohol and cholesterol are also quoted for a comparison. A standard was 0.01025n. KOH aq. solution.
A.G. means % of acid esterified after one hoyr at 155°.
Phenylacetic
acid, mg.
6.38
6.07

Alkali,
cc.
3.27
1.91

A.G.

Per hydrokitol

Sample,
mg.
9.04
10.73

Cetyl
alcohol

14.82
12.41

6.89
7.00

2.62
2.10

39.0
58.8

Cho lesterol

12.09
12.366.94
7.09

4.50
4.04

15.8
33.6

43.7
68.9

7. Rate of Esterification of Perhydrokitol with Phthalic Anhydride.-After somany preparatory experiments on cetyl alcohol and cholesterol, the author found thefollowing method to discriminate primary alcohol from secondary one : almost same
method as the determination of hydroxyl group in experiment 5, except the reaction
temperature kept at 10G 0 for one and thirty hours.
Alkali,
cc.
1.00
2.10
0.07

OH(corr.) %After Perhydrokitol
1 hr.
Cetyl alcohol
Cholesterol

Sample,
mg.
10.60
13.00
15.30After Perhydrokitol
SO hrs. Cetyl alcohol
Cholesterol

12.00
15.50
16.70

4.00
7.90
3.67

5.72
8.85
3.44

1.45
2.61
0.0

From above data the percentage of OH% after 1 hr. to OH% after 30 hrs. wascalculated as follows: perhydrokitol 25.4, cetyl alcohol 25.5, cholesterol 0.0.

198

Y. OMO'fE

Summary
From the expriments on the hydrogenation curve and the -addition
with maleic anhydride of chromatographically pure kitol, the author.:Presumed four conjugated double bonds containing one in the ring andproved that they reacted with maleic anhydride.
Esterification of perhydrokitol prepared from kitol through hydrogenation, when treated with phenylacetic acid at 155° for one hour,
showed that perhydrokitol is a primary alcohol. The fact was also
. confirmed by the method to measure the esterification rate of an
alcohol with phthalic anhydride in pyridine at 100°.

References
1) N.D. Embree, E.M. Shantz, J. Am. Chem. Soe., 65, 910 (1943).
· 2) F.B. Clough, H.M. Kascher, C.D. Robeson, J.G. Baxter, Scierwe, 105, 436 (1947).
3) S. Ishikawa, Y. Omote, M. Kijima,. H. ~kuda, Sci. Rep. Whales Research Inst.,
No. 5, 61 (1951).
4) Y. Omote, J. Chem. Soe. Japan, Ind. Chem. Seet., 54, 589 (1951).
· 5) R.K. Barua, R.A. Morton Biochem. J. 45, 308 (1949).
6) H.A. Nash, F.W. Quackenbush, J.W. Porter, J. Am. Chem. Soe., 70, 3613 (1948).
'7) K. Dimroth, Angsw. Chem., 52, 545 (1939).
8) S. Murahashi, Sc. Pap. I.P.C.R. (Japan), 30, 2'72 (1936).
9) H. Nobori, T. Yamada, J. Chem. Soa. Japan, Ind. Chem. Seet., 47, 15 (1944).
10) ·s. Siggia, I.R. Kervenski, Anal. Chem., 23, 11'7 (1951).