bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure of Radicals Produced by γ-Radiolysis. Part 2. Radicals Derived from 5-Membered Alicyclic Molecules
Authors: Linder Ron E. , Ling A. Campbell
Published: May 2006

Data are presented for the results of γ-radiolysis on cyclopentane, methyl cyclopentane, cyclopentene, and cyclopentadiene, held as solutes in adamantane matrices. Data from this particular matrix isolation technique are in accord with liquid phase studies for cyclopentane and cyclopentene, and indicate that tertiary hydrogen loss occurs in methyl cyclopentane, and that cyclopentadiene yields at least three radicals. Two of the radicals derived from cyclopentadiene have been identified as the C5H5•entity with five equivalent protons, and the [Formula: see text] allylic-type radical formed by hydrogen atom addition to molecular C5H6.
Chemical Syntheses of α-Linked Disaccharides
Authors: Lemieux R. U. , James K. , Nagabhushan T. L.
Published: May 2006

Chemical syntheses of six α-linked disaccharides are described, namely, 6-O-(α-D-glucopyranosyl)-D-galactose (1), 6-O-(α-D-galactopyranosyl)-D-galactose (2), 6-O-(α-D-talopyranosyl)-D-galactose (3), 3-O-(α-D-glucopyranosyl)-D-glucose (nigerose) (4), 3-O-(α-D-galactopyranosyl)-D-glucose (5), and 3-O-(α-D-talopyranosyl)-D-glucose (6).
The Synthesis of Kanamycin Analogs I. α-D-Glucopyranosyl Derivatives of Deoxystreptamine
Authors: Lemieux R. U. , Nagabhushan T. L. , Clemetson K. J. , Tucker L. C. N.
Published: May 2006

The procedure developed in this laboratory for the synthesis of α-D-glucopyranosides based on the reaction of dimeric tri-O-acetyl-2-deoxy-2-nitroso-α-D-glucopyranosyl chloride with alcohols was employed to synthesize the three α-D-glucopyranosyl deoxystreptamines and 4,6-di-O-α-D-glucopyranosyl deoxystreptamine. Effects of pH change on the n.m.r. spectra of kanamycins A and B and of the above synthetic compounds are interpreted in terms of a conformational change.
Rearrangements in the Diterpenoid Series. I. The Solvolysis of Methyl 15β-tosyloxy-13-isopropyl-17-noratis-13-en-18-oate
Authors: Ayer William A. , Deshpande Pandurang D.
Published: May 2006

The synthesis of methyl 15β-hydroxy-13-isopropyl-17-noratis-13-en-18-oate (14b) is described. Compound 14b was prepared from the ketone 12b, in turn derived from the Diels–Alder adduct formed between levopimaric acid (7) and α-acetoxyacrylonitrile. Solvolysis of the tosylate of 14b proceeds predominantly with rearrangement and elimination to give methyl 16-isopropylidene-7,17-secoacon-8(15)-en-18-oate (16a). This rearrangement serves as a model for the proposed biosynthetic transformation of atisine-type alkaloids into alkaloids of the aconitine series. The degradation of 16a into the unsaturated ketone 19, which contains the 19 carbons of the aconane skeleton, is described. The Diels–Alder addition of methyl vinyl ketone to levopimaric acid is reported and the adduct is shown to possess structure 8.
Mass Spectra of Some Sulfinate Esters and Sulfones
Authors: Baarschers W. H. , Krupay B. W.
Published: May 2006

The mass spectra of some alkyl arenesulfinates were found to be distinctly different from the spectra of the isomeric aryl alkanesulfinates. Both classes of compounds in turn could easily be distinguished mass spectroscopically from the sulfones with which they are isomeric. The preparation of a new aryl alkanesulfinate, CH3S(O)OC6H4CH3, is described.
The 2,2,2-Trichloroethyl Group for Carboxyl Protection During Peptide Synthesis
Authors: Marinier Bernard , Kim Yoon C. , Navarre Jean-Marie
Published: May 2006

The 2,2,2-trichloroethyl esters of several N-carbobenzoxy-amino acids were prepared by reacting the corresponding acid chlorides with trichloroethanol and the carbobenzoxy groups were selectively removed by HBr–AcOH. The resulting esters were then coupled with various N-carbobenzoxy-amino acids or peptides using dicyclohexylcarbodiimide in acetonitrile to give N-carbobenzoxy-peptide trichloroethyl esters. The selective removal of the trichloroethyl protecting group was effected by reduction using zinc in acetic acid. The optical activity of the N-carbobenzoxy-peptides so obtained agreed well with the values reported in the literature. The overall results suggest that the 2,2,2-trichloroethyl group could be useful for carboxyl protection during peptide synthesis.
Etude des dérivés sulfohydroxylés des halogénures de bore et des cycles dérivés du borsulfol I. Synthèses et mécanismes réactionnels
Authors: Bouix Jean , Hillel Roger
Published: May 2006

By the action of H2S on boron halides (other than fluoride) one obtains the new substitution products BX2SH, BX(SH)2, and B(SH)3 along with the corresponding hydrogen halide. These halogenosulfhydroboranes are unstable and cyclize to cyclic boron sulfides, either (BSSH)3 or (BSX)3.In the case of boron bromide it is possible, by controlling the ratio of the reactants and the temperature of the reaction, to promote the formation of one of the three possible substitution products. Then by encouraging cyclization one may obtain, rapidly and selectively, either (BSSH)3 or (BSBr)3.Synthesis of (BSCl)3 was accomplished by dissolution of (BSSH)3 in liquid BCl3 and that of (BSI)3 by the action of H2S on solid BI3. [Journal translation]
Semimicro Determination of Sugar Configuration by Measurement of Circular Dichroism of Alditol Acetates
Authors: Bebault G. M. , Berry J. M. , Choy Y. M. , Dutton G. G. S. , Funnell N. , Hayward L. D. , Stephen A. M.
Published: May 2006

The configuration (D or L) of a sugar may be determined conveniently by circular dichroism measurements at 213 nm on alditol acetates, or their methylated derivatives, where the acetoxy group acts as a chromophore. Only milligram quantities of material are required and the method is well suited to analyzing fractions obtained by gas–liquid chromatography. Structural information which may be derived from the c.d. spectra is briefly discussed.
Formation and Reactions of (1-Chloroalkyl)carbamoyl Chlorides. Synthesis of 1,2,4-Triazolidine-5-ones
Authors: Koyano Kinko , McArthur Colin R.
Published: May 2006

N-(α-Chlorobenzyl)carbaniloyl chloride and (α-chlorobenzyl)methylcarbamoyl chloride are formed by reaction of phosgene with N-benzylideneaniline and N-benzylidenemethylamine, respectively. Reaction of these carbamoyl chlorides with a number of nucleophiles is described, some of which cause cleavage of the benzyl to nitrogen bond while others give rise to substitution products without such cleavage. Of the latter type, substituted hydrazines react to effect ring closure to1,2,4-triazolidine-5-ones. The method serves as a convenient synthesis of these new heterocyclic systems.
Synthesis and Characterization of Dipyrazolylalkanes, and Some of Their Complexes With CoCl2
Authors: Thé K. I. , Peterson L. K.
Published: May 2006

The reaction of dipyrazol-1-yl ketone with appropriate ketonic compounds is catalyzed by the presence of CoCl2, to yield dipyrazolylalkanes (C3H3N2)2CRR′, (a) where R = R′ = CH3, CD3, C2H5; (b) where R = H, R′ = CH3, C6H5; (c) where R = CH3, R′ = C2H5; and 1,1-dipyrazolylcycloalkanes derived from cyclobutanone, pentanone, hexanone, 3-methyl and 4-methylhexanone. Cobalt(II) chloride reacts with dipyrazol-1-yl ketone, in tetrahydrofuran, to yield the complex CoCl2(C3H3N2)2CO, and in acetone or acetone-d6 to yield CoCl2(C3H3N2)2C(CH3)2 or CoCl2(C3H3N2)2C(CD3)2.
Nitrilohexaphosphonitrilic Chloride: A Chemical and Spectroscopic Study
Authors: Oakley R. T. , Paddock N. L.
Published: May 2006

The preparation of nitrilohexaphosphonitrilic chloride N7P6Cl9 is described; its infrared, Raman, mass and nuclear magnetic resonance spectra indicate a tricyclic condensed ring structure of C3ν symmetry. The molecule decomposes on attempted substitution of the chlorine atoms by fluorine and by methoxy-groups, but with dimethylamine both addition and substitution take place. One central bond is broken, and a bridged ring imide N6P6(NH)(NMe2)8Cl2 is formed, in which the ring structure is sufficiently rigid for axial and equatorial groups to be distinguished. The detailed molecular structure of N7P6Cl9 shows evidence of a compromise between the requirements for optimum σ- and π-bonding, the central N—P bonds being strained. Its substitution behavior, base strength, ultraviolet spectrum, mass spectrum, and molecular geometry are interpreted in these terms.
Proton Magnetic Resonance Studies of Long-range Coupling Constants: Conformational Dependence of the 4J Coupling Between Side Chain and Ring Protons in Formylheterocycles
Authors: Roques Bernard Pierre , Combrisson Suzanne
Published: May 2006

The 4J coupling constant between side chain and ring protons is studied on particular models of planar heterocyclic aldehydes.The preferential conformation of these molecules is established by use of the "zig–zag" rule for the 5J coupling constant. This allows precise analysis of the 4J coupling across cc and ct pathways.The sign of some of these constants is determined and is found to be negative in either cc or ct pathways. The use of the "methyl replacement technique" shows a dominant σ electron contribution to the 4J coupling constants. In all examples studied here, the 4J coupling value is dependent on the pathway: 4Jct (−0.30 at −0.45 Hz) > 4Jcc (−0.10 at −0.15 Hz). The existence of a stereospecificity for this coupling is in accordance with a preponderant σ electron mechanism and is useful in conformational analysis of planar aromatic aldehydes.
Reactions of Thiyl Radicals. X. Photolysis of Ethyl Sulfide Vapor
Authors: Smith Conrad S. , Knight Arthur R.
Published: May 2006

The photolysis of ethyl sulfide vapor at 2537 Å has been investigated as a function of substrate and CF4 pressure, time, and temperature. Reaction products with quantum yields in parentheses are ethyl disulfide (0.178), ethane (0.138), butane (0.086), ethanethiol (0.096), 4-methyl-3-thiahexane (0.034) and 4-methyl-3,5-dithiaheptane.Ethyl and ethylthiyl radicals are formed in the primary process and the product yields indicate a net primary decomposition quantum yield of 0.48. A reaction mechanism involving subsequent reactions of the primary fragments is proposed and explains the observed products and the observed variation in rates. Excited radicals and hot radical combination products play a minor role in this system, in contrast to the behavior of lower molecular weight sulfides. Secondary photolysis of the disulfide produced and consumption of ethanethiol are important factors in determining the time dependence of reaction rates in this system.
Raman Spectra of Hexagonal Ethylsulfates of Yttrium and of some Rare Earths
Authors: Schaack G. , Koningstein J. A.
Published: May 2006

The phonon Raman spectra of single crystals of Y(C2H5SO4)3•9H2O, Ce(C2H5SO4)3•9H2O, Nd(C2H5SO4)3•9H2O, Sm(C2H5SO4)3•9H2O have been studied at low temperatures with laser excitation. Some information has also been obtained of the compounds of Ho3+ and Er3+. The types of symmetry of the observed modes have been determined and compared with the results of a group theoretical calculation. The internal modes of the C2H5 and SO4 groups and of the H2O molecules can be completely attributed to observed transitions. There is some evidence to attribute the librational modes of the H2O molecules to transitions which show a very pronounced temperature dependence of the line-widths. Reasons for this temperature dependence are discussed. No lines have been found that can be attributed uniquely to electronic transitions.
Conformational Preferences of ortho-Substituted Benzophenones. Correlations Between Carbon-13 Nuclear Magnetic Resonance Shieldings and Calculated Torsional Angles
Authors: Buchanan Gerald Wallace , Montaudo Giorgio , Finocchiaro Paulo
Published: May 2006

The results of an investigation of the conformational properties of some benzophenones are reported. Carbon-13 n.m.r. spectra provide a generally applicable method to study the conformational preference of these compounds through the C=O shifts. Semi-empirical conformational energy calculations have been used to build contour maps of relative conformational energy as a function of the two internal rotation angles of these molecules. Conformations of minimum energy, as detected from the contour maps, have been assumed as the most stable. The phenyl torsional angles corresponding to these conformations, plotted against the C=O shifts, furnish linear relationships.
A Proton Magnetic Resonance Study of the Effect of 2′-O-Methylation on Ribonucleoside Conformation
Authors: Hruska Frank E. , Mak Alan , Singh Harwant , Shugar David
Published: May 2006

The 100- and 220- MHz p.m.r. spectra of uridine, cytidine, and their 2′-O-methyl derivatives are obtained in aqueous solution at several temperatures. The experimental chemical shifts and coupling constants are discussed in terms of the overall molecular conformation. The conclusion is reached that 2′-O-methylation has little effect upon the three-dimensional structure of a nucleoside at the monomer level in an aqueous environment.
A Study of Thermal Motion of Ammine Groups in Carbonatotetramminecobalt(III) Sulfate
Authors: Dunell B. A. , Pachal M. D. , Ulrich S. E.
Published: May 2006

The results of spin–lattice relaxation measurements are reported for carbonatotetramminecobalt(III) sulfate. The observed TI minima and activation energies, 1.9 and 4.3 kcal, for the reorientation of ammine groups are interpreted on the basis of hydrogen bonding effects.
Radical Substitutions of Azo Compounds
Authors: Lui Henry , Warkentin John
Published: May 2006

Treatment of γ-(p-nitrophenylazo)-γ-valerolactone with benzoyl peroxide in benzene at 85°, yields p-nitroazobenzene and p-nitrobiphenyl. Similarly, α-methyl-α-phenylazotetrahydrofuran yields azo-benzene. Radical substitution at azo nitrogen and at N-bearing benzenoid carbon are the suggested mechanisms. Such reactions of aryl azo compounds have not been reported previously.
On the Assignment of the Infrared Spectrum of Ethylene Oxide
Authors: Bertie John E. , Othen David. A.
Published: May 2006

In the infrared spectrum of gaseous ethylene oxide the A1 C—H stretching and CH2 wagging modes are assigned at 3018 and 1148 cm−1, respectively. The previous assignment of the B1 ring deformation mode at about 890 cm−1 is not consistent with the spectrum, but its correct assignment is not clear. The infrared spectrum of ethylene oxide liquid and the frequencies of the fundamental modes in the gas and liquid states are presented.
Correlation between the Electrochemical and Spectroscopic Behavior of some Substituted Pyridines
Authors: Loutfy Rafik O. , Loutfy Raouf O.
Published: May 2006

The n,π* triplet energies of pyridine, 2-, 3-, 4-cyano, and 2,6-dimethylpyridines were found to correlate linearly with the corresponding half-wave potentials, E1/2. Similar relationship was obtained for acetophenone, 2-, 3-, and 4-acetylpyridines as well as for benzophenone, 2-, 3-, and 4-benzoylpyridines. The latter relationships indicated that the n → π* transition of the benzoyl and acetylpyridines must involve the n-electron of the carbonyl oxygen.
The Mechanism of the HgH A22Π3/2 → X2Σ+ Emission in the Hg(63P0) Photosensitization of Hydrogen and the Alkanes
Authors: Vikis A. C. , Roy D. J. Le
Published: May 2006

The mechanism of the HgH A22Π3/2 → X2Σ+ emission detected in the Hg(63P0) photosensitized decomposition of H2 and some of the lower alkanes, RH, was investigated. It was concluded that ground state HgH was formed in the primary process Hg(63P0) + RH(or H2) → HgH(X2Σ+) + R(or H). The HgH A22Π3/2 → X2Σ+ emission and presumably the A12Π1/2 → X2Σ+ and B2Σ+ → X2Σ+ emission, also observed in the above systems, result from secondary excitation of ground state HgH on collision with Hg(63P0). Studies of the emission made possible the estimation of relative quantum yields for the above primary process.
Crystal and Molecular Structure of Potassium trans-1,2-Diaminocyclohexane-N,N′-tetraacetatomanganate(III) Monohydrate, K[Mn(DCTA)]•H2O
Authors: Rettig Steven J. , Trotter James
Published: May 2006

Crystals of the title compound are triclinic, a = 15.60(3), b = 8.66(2), c = 7.36(1) Å, α = 103.8(1), β = 95.7(1), γ = 70.7(3)°, Z = 2, space group [Formula: see text]. The measured and calculated densities are 1.69(2) and 1.656(6) g cm−3, respectively. The structure was determined by Patterson and Fourier synthesis and refined by full-matrix least-squares procedures to a final R of 0.067 for 2333 observed reflections. The structure is composed of layers of oxygen bridged potassium ions situated between two layers of [Mn(DCTA)]− anions, thus forming the basic structural unit which repeats along a. The manganese(III) is six-coordinated to the two nitrogen and four oxygen atoms of the hexadentate ligand, the coordination polyhedron being a very distorted octahedron with N—Mn—O and O—Mn—O angles of 77.1(2) and 128.5(2)°, respectively. The anion has approximate C2 symmetry with two classes of Mn—O bonds, mean bond lengths 1.887(7) and 2.015(22) Å; the mean Mn—N distance is 2.263(5) Å. The water molecule is twofold disordered and is coordinated to the potassium ion in both positions. The potassium ion is eight or nine coordinated to oxygen atoms depending on the position taken by the water molecule. Weak hydrogen bonds involving the water molecule are probably present, O…O distances range from 2.71(3) to 3.18(3) Å, as well as possible C—H…O hydrogen bonds with C…O distances ranging from 3.300(9) to 3.388(8) Å.
A Theoretical Study of the Site of Protonation of Formamide Using Non-empirical LCAO-MO-SCF Calculations
Authors: Hopkinson Alan C. , Csizmadia Imre G.
Published: May 2006

Molecular orbital calculations are used to show that O-protonated formamide is more stable than its N-protonated tautomer by 6.2 kcal/mol. The computed proton affinity of formamide (assuming O-protonation) is computed to be 254.8 kcal/mol.
Synthesis and Rearrangement Control of Substituted Benzobicycloheptane Aziridines
Authors: Wiesner K. , Ho Pak-Tsun , Jain R. C. , Lee S. F. , Oida S. , Philipp A.
Published: May 2006

A general synthesis of various substituted benzonorbornene derivatives is described. Benzenesulfonyl aziridines of these compounds were prepared and their acetolysis was studied. The influence of various substitution patterns on the direction of the aziridine rearrangement is discussed and it is shown that the rearrangements may be used as a convenient approach to the synthesis of ring B bridged diterpene alkaloids. Considerable general synthetic utility of these techniques is anticipated.
Aromatic Substitutions with Carbanion Nucleophiles. II. The Kinetics and Mechanism of the Reaction of 1-Fluoro-2,4-dinitrobenzene with the Diethyl Malonate Anion
Authors: Leffek Kenneth T. , Tremaine Paul H.
Published: May 2006

The reaction of fluoro-2,4-dinitrobenzene with the sodium salt of diethyl malonate to form diethyl (2,4-dinitrophenyl)malonate is fast in dimethyl sulfoxide solvent. The stable red color of the reaction solution is due to the anion of the product, although the initially formed unstable intermediate between the substrate and the anion nucleophile is also red and can be observed at times less than 200 ms after mixing.The rate constants for all the steps in the reaction have been measured and the activation parameters for the three processes involved in the nucleophile substitution have been calculated.
Base-catalyzed Isotopic Exchange of Molecular Hydrogen. II. Rate Dependence on Basicity in the Dimethyl Sulfoxide–Water System
Authors: Symons E. Allan , Buncel Erwin
Published: May 2006

Isotopic exchange of D2 has been determined in mixtures of dimethyl sulfoxide and water under catalysis by hydroxide ion. The rate of exchange increases by ca. 104 as the medium composition is changed from 0% DMSO to 99.6% DMSO at 65 °C. The unusually low sensitivity to medium basicity is reflected in abnormally low slope values for the plots of log kobs υs. H− or J−. When [Me4NOH] is varied at a given medium composition, the apparent order with respect to [Me4NOH] is greater than unity.These results are discussed in terms of (1) rate determining proton transfer from D2 to OH− with formation of hydride ion; (2) a concerted reaction of OH−, D2, and H2O; (3) addition of OH− to D2 to yield an intermediate adduct, [HODD]−; (4) a 6-centered process involving cation participation and electrophilic assistance by H2O in the reaction of OH− with D2.L'échange isotopique de D2 a été étudié dans des mélanges de sulfoxyde de diméthyle et d'eau sous l'effet d'une catalyse par l'ion hydroxyle. Le taux d'échange augmente d'environ 104 alors que la composition du milieu change de 0% en DMSO à 99.6% en DMSO à 65 °C. La sensitivité anormalement faible à la basicité du milieu est réflétée par des valeurs anormalement faibles de la pente dans les graphiques du log kobs υs. H− ou J−. Quand la concentration de Me4NOH est changée pour une composition donnée du milieu, l'ordre apparent en ce qui a trait à la [Me4NOH] est plus élevé que l'unité.
Photooxidation and Reduction of Ascorbic Acid Studied by E.S.R.
Authors: McAlpine Robert D. , Cocivera Michael , Chen Holger
Published: May 2006

The photooxidation of ascorbic acid in water at pH 4.5–11.6 was studied using electron spin resonance spectroscopy. In the presence of oxygen, only one radical is detected and its resonance lines are broad. In the absence of O2, better resolution is obtained and a second radical is observed. When N2O or H2O2 is added, the second radical disappears while the concentration of first radical is increased. These results are consistent with a primary photochemical step involving ejection of an electron from the monoanion of ascorbic acid to form the ascorbate. The second radical appears to be formed by addition of a hydrated electron to the monoanion of ascorbic acid.
Sur la conformation des tert-butylcyclohexanes substitués en position 2
Authors: Richer Jean Claude , Freppel Christian , Tchapla Alain , Welvart Zoltan
Published: May 2006

Examination of the pKMCS(80% methylcellosolve) of amino alcohols and amines derived from tert-butylcyclohexane shows that introduction of a tertiary butyl group in the adjacent position to a hydroxyl leads, by comparison to the non-substituted cyclohexanol, to a flattening of this portion of the ring when the hydroxyl and tert-butyl groups are trans; when the groups are cis a straightening occurs.
An Investigation into the Nature of π-Inductive Effects: π Polarization Effects in Phenylalkanes with Polar or Charged Substituents
Authors: Reynolds W. F. , Peat I. R. , Freedman M. H. , Lyerla Jr J. R.
Published: May 2006

pH dependent 13C chemical shifts for phenylglycine, phenylalanine, and phenylalanyl derivatives demonstrate that the electronic distribution of the phenyl group depends upon the distance of charged groups from the phenyl ring. The pattern of chemical shifts and the results of CNDO/2 MO calculations indicate that this is due to polarization of the phenyl π electron system. 13C chemical shifts and CNDO/2 calculations for α- and β-substituted phenylalkanes (substituent = NH3+, Cl or Br) provide further evidence for a π polarization effect.
Fragmentation and Rearrangement Processes in the Mass Spectra of Perhalogenoaromatic Compounds. Part IX. Pentafluorophenol and Pentafluorothiophenol Derivatives of Group IV
Authors: Lanthier G. F. , Miller J. M. , Oliver A. J.
Published: May 2006

The mass spectra of R3MSC6F5 and R3MOC6F5 (R = CH3 or C6H5; M = Si, Ge, Sn) are reported and compared with the corresponding pentafluorophenyl derivatives. The sulfur and oxygen compounds show fewer rearrangements leading to the formation of metal fluorides than do simple C6F5 derivatives. The ions R3M+ are usually observed as the base peaks. Ions containing Sn—S appear more stable than Sn—O species, while the reverse seems true for silicon.
Silyl-substituted α,β-Unsaturated Ketones from the Reaction of Silylvinylmetallic Reagents with Acid Anhydrides
Authors: Brook A. G. , Duff J. M.
Published: May 2006

The reactions of a series of silyl-substituted vinylmetallic reagents with acetic and benzoic anhydride have been investigated as a general route to α,β-unsaturated ketones having a silyl group attached to the carbon–carbon double bond. The reaction has been found to be generally applicable for acetyl derivatives provided low temperatures are used but the reaction with benzoic anhydride gives poorer results. The i.r. and u.v. spectra of the ketones are discussed. The characterization of novel 1,4-dienes obtained as by-products in the syntheses is also described.
Effect of Pressure on the Rates of Reaction of Hydrogen Atoms in the Radiolysis of Liquid Ethanol
Authors: Jha Kamal N. , Freeman Gordon R.
Published: May 2006

Competition between the reactions[Formula: see text]and[Formula: see text]was measured at 296 K at 1 bar and 5.4 kbar. Values of k5/k3 at 1 bar and (ΔV5≠ − ΔV3≠) averaged between 1 bar and 5.4 kbar for several solutes S are: cyclohexene, 56, + 2.7 cm3/mol; hexene-1, 71, + 2.6 cm3/mol; phenol, 25, −3.8 cm3/mol; benzene, 12, −6.5 cm3/mol. The volume of activation of hydrogen atom addition to the aromatic ring is about 8 cm3/mol more negative than that of addition to a mono-olefin. Rate constants of reaction of solvated electrons with these solutes at 295 K, measured by the pulse-radiolysisspectroscopy technique, are (M−1 s−1): cyclohexene, <1 × 104; hexene-1, 1 × 105; benzene, 4 × 106; phenol, 5 × 107. The phenol reaction with e−solv does not reduce the hydrogen yield by a proportionate amount, so phenol "catalyses" the decomposition of e−solv to form hydrogen, perhaps via C6H5OH−solv → C6H5O−solv + H. The scavenging of hydrogen precursors by hexene-1, benzene, and aniline in n-hexane, reported in ref. 6, had [Formula: see text], −6, and −4 cm3/mol, respectively, all three of which may be attributed to hydrogen atom reactions. The yields of hydrogen from solutions of neohexane in cyclopentane at 1 bar and 5.4 kbar indicate that charge transfer occurs from cyclopentane to neohexane, and that the probability of charge transfer is independent of pressure. The methane yields from these solutions indicate that the decomposition of the neohexane ion formed by charge transfer from cyclopentane, to form methane, is inhibited by pressure.
The Bonding of a Silicon Atom with a Phenyl Ring: the Photoelectron Spectrum of Phenylsilane
Authors: McIean Ronald Allan Neill
Published: May 2006

The first band in the photoelectron spectrum of phenylsilane, which is caused by two ionization processes, is shifted to higher energy compared with the corresponding band in the carbon analog, toluene. In particular the highest energy orbital of phenylsilane appears to be stabilized compared to that in toluene probably due to (p → d) π bonding.
The Position of Phosphate Groups in the Phosphonomannan of Hansenula capsulata, as Determined by Carbon-13 Magnetic Resonance Spectroscopy
Authors: Gorin Philip A. J.
Published: May 2006

The carbon-13 magnetic resonance spectrum of a phosphate of 2-O-β-D-mannopyranosyl-α,β-D-mannose was compared with that of the unphosphorylated disaccharide. The positions and number of the signals of C-5's which are coupled to phosphorus-31, together with other spectral data show that the phosphate group is on C-6 of the reducing end-unit (2, Fig. 1). This differs from a previous assignment (1), thus necessitating a revision (4) to the structure 3 proposed for the parent Hansenula capsulata phosphonomannan.
Dielectric Constant, Density, and Enthalpy of Transition of Cyclohexane and Neopentane at 500 Atmospheres
Authors: Chew Hemming Art-Ming , Chan Raymond Kai-Chow
Published: May 2006

A cell has been described for the simultaneous measurement of the dielectric constant and volume changes at the phase transition of solids at low temperatures and pressures up to 500 atm. The dielectric constants of the high temperature phase of cyclohexane and neopentane at 10 kHz increase with decreasing temperature according to the Clausius–Mossotti equation. The low temperature solid phase of both non-polar substances has considerably high shear strength and it is suggested that the dielectric data of these substances in the literature may have considerable errors. The enthalpies of fusion and solid–solid transition at 500 atm have been calculated from the experimental results.
Comment: Concerning the Paper of R. P. Mariella and K. H. Brown "A Novel SN1 Displacement: The Reaction of Tertiary Amines with Acetic Anhydride"
Authors: Gol'dfarb Ya. L. , Belen'kii L. I.
Published: May 2006

The remarks on the paper of Mariella and Brown (1) concern three points: (1) some similar data from the literature were not mentioned; (2) the mechanism proposed does not take into account the possibility of catalysis of the reaction; and (3) the interpretation of the process as SN1 displacement is not compatible with known data.
Photochemistry of 2,4-Cyclooctadienone. II In Neutral and Acidic Methanol
Authors: Lange Gordon L. , Neidert Eli
Published: May 2006

Irradiation of 2,4-cyclooctadienone (1) in neutral dry methanol resulted in the formation of 3-methoxy-4-cyclooctenone (18%) and two head-to-head 2 + 2 dimers (combined yield 64%). A similar irradiation in acidic methanol (0.001 N HCl) caused a dramatic change in the products formed. A new compound, the dimethyl ketal of trans, cis-2,4-cyclooctadienone was formed in 67% yield along with the two dimers (<10%). A mechanism is proposed whereby the photochemically derived trans, cis-2,4-cyclooctadienone reacts in thermal processes to give the products described. Low temperature trapping experiments which support this hypothesis are discussed.
Comment: Reply to Primet and Mathieu Concerning the Infrared Observation of PtOH Species
Authors: Morrow B. A. , Ramamurthy P.
Published: May 2006

The i. r. absorption bands due to CaCl2 hydrates, formed on CaF2 windows during the preparation of silica supported platinum from H2PtCl6, should not be confused with those of surface Pt—OH species which are formed by other methods.
Synthesis of Phenols from Diazonium Tetrafluoroborates; a Useful Modification
Authors: Horning D. E. , Ross D. A. , Muchowski J. M.
Published: May 2006

It is shown that phenols are obtained in good yield by the decomposition of aromatic diazonium tetrafluoroborates in refluxing trifluoroacetic acid containing potassium trifluoroacetate.
Five-membered Heterocyclic Thiones. Part IV. 1,2,4-Thiadiazole-3-thiolates and 1,2,4-Thiadiazole-5-thione
Authors: Lacasse G. , Muchowski J. M.
Published: May 2006

1,2,4-Thiadiazole-5-thione (2a) was synthesized from the corresponding 5-bromo compound. An alternative synthesis of the known 3-methyl-1,2,4-thiadiazole-5-thione is described. It was shown by i.r. spectroscopy that the parent compound and its 3-methyl derivative existed in the thione form in the solid state.Mercuric-1,2,4-thiadiazole-3-thiolate (5) was prepared by cleavage of the corresponding disulfide with mercury. The mercuric salt was converted to a stable (in solution) sodium salt, but the free thio compound was not isolable.
On the Mechanism and Substituent Effects of the Tl(III) Oxidation of Phenylethylenes in Methanol
Authors: Nadon L. , Tardat M. , Zador M. , Fliszar S.
Published: May 2006

The oxidation of phenylethylenes by Tl(NO3)3 in methanol proceeds rapidly and selectively to give the products resulting from the migration of aryl groups, i.e., (i) the 1,1-dimethoxy-2-phenylethanes from the corresponding styrenes, (ii) the phenylacetones from the α-methylstyrenes, and (iii) the two possible deoxybenzoines from the 1,1,-diphenylethylenes. The kinetic results, which indicate the formation of the thallic–organic intermediate to be the rate determining step, are discussed in terms of the mechanism of reaction and show the role of the coordination of Tl(III). Hammett's relationship, with ρ = −4.2, describes the substituent effects for the competitive oxidation of ring-substituted styrenes and α-methylstyrenes. The relative migratory aptitudes of aryl groups, as determined from the oxidation products of ring-substituted 1,1-diphenylethylenes, is correlated to Brown's σ+ constants, with ρ+ = −2.27.
Dakin Oxidation of o-Hydroxyacetophenone and some Benzophenones: Rate Enhancement and Mechanistic Aspects
Authors: Hocking M. B.
Published: May 2006

A synthetic aqueous alkaline hydrogen peroxide solution, made up to approximate the concentrations of caustic and hydrogen peroxide expected from water washing of aerated sodium amalgam, readily oxidized o-hydroxyacetophenone to catechol. The relevance of a proposed ester intermediate of this reaction is discussed, and also the possibility of using o-hydroxybenzophenone (originating from phenylben-zoate) as a substrate is briefly considered.
Synthesis of Nucleotides from 8,2′-Thioanhydropurine Nucleosides
Authors: Ogilvie Kelvin K. , Slotin Lewis A.
Published: May 2006

The 5′-mono and diphosphates of the common 8,2′-thioanhydropurine nucleosides have been prepared and studied with 5′-nucleotidase. alkaline phosphatase, and adenylate kinase. Procedures for the preparation of protected anhydronucleosides and their incorporation into dianhydronucleoside monophosphates have been developed. These nucleotides have been found to be completely resistant to spleen and snake venom phosphodiesterases but are readily converted with Raney nickel into the natural 2′-deoxy-nucleotides.
The gauche Effect. A Theoretical Study of the Topomerization (Degenerate Racemization) and Tautomerization of Methoxide Ion Tautomer
Authors: Wolfe Saul , Tel Luis M. , Csizmadia I. G.
Published: May 2006

Non-empirical double zeta quality molecular orbital calculations on −CH2OH as a function of the C—O bond length (r), the rotational angle about the C—O bond (θ), and the pyramidal angle at carbon [Formula: see text] are described. From the stretching potential curve, E(r), it is shown that dissociation of −CH2OH proceeds to give CH2 and OH−. The rotation–inversion surface, [Formula: see text], has two types of minima; in both cases the most favorable pyramidal angle at carbon is 105°. The lower minimum corresponds to a structure (the Y conformation) having the hydroxyl proton on the external bisector of the HCH angle. The higher minimum is 6.67 kcal/mol less stable and corresponds to a structure (the W conformation) having the hydroxyl proton on the internal bisector of the HCH angle. The relationship of these results to the gauche effect is discussed and it is noted that at certain internuclear distances the nuclear–nuclear repulsion term (Enucl) may overcome the tendency of adjacent electron pairs and polar bonds to exist preferentially in that conformation which has the maximum number of gauche interactions between these electron pairs or polar bonds.The topomerization of −CH2OH, i.e., the conformational transformation from one Y conformation into another, proceeds, via the W conformation as an intermediate, by two separate events, viz. rotation about the C—O bond, having a barrier of 10.58 kcal/mol, and pyramidal inversion at carbon, with a barrier of 20.52 kcal/mol. Some factors governing the relative importance of rotation and inversion in degenerate racemization are discussed.In its ground electronic state CH3O− is 22.18 kcal/mol more stable than −CH2OH. However, in the low-lying excited states all conformations of −CH2OH are stabilized relative to CH3O−. The most stable excited state structure of −CH2OH corresponds to the energy maximum for rotation–inversion of the ground electronic state.
Free-energy Relationships in Coordination Chemistry. III. A Comprehensive Index to Complex Stability
Authors: Nieboer E. , McBryde W. A. E.
Published: May 2006

Efforts to relate metal-complex stability constants to some property of the metal ions involved have led to the development of a correlating numerical index Q with the following characteristics: (i) Q is a two parameter quantity involving ionic charge and electronegativity, which may assume different values for a particular metal according to the type of ligand with which complexes are formed; (ii) linear relationships are obtained for plots of log KMLvs. Q for various metals and more than thirty ligands. The effect of the thermodynamic and structural properties of ligands and metal complexes on the slope and intercept in this correlation is discussed. Two new indices to class b behavior are introduced, one for metal ions and one for ligands. The index Q is shown to be related to other published indices of ionic or covalent, class a or class b, behavior of metals and ligands; the alternative ways of assigning Q may be regarded as reflecting the varying degrees of ionic or covalent character in the complexes of a given metal.
Determination of the Basicities of a Series of Substituted Benzyldimethylamines in 50% Aqueous Methanol
Authors: Lee Donald G. , Srinivasan R.
Published: May 2006

The basicities of a series of substituted benzyldimethylamines have been determined potentiometrically in 50% (by weight) aqueous methanol. An excellent Hammett correlation (ρ = −1.38) is obtained. The larger value of ρ in aqueous methanol as compared to water (−1.14) is interpreted in terms of a greater capability of water to solvate ammonium ions, thus suppressing the stabilizing or destabilizing effect of ring substituents.
Proton N.M.R. Spectra of some Cyclopentadienyltitanium Compounds
Authors: Glivicky Alexandr , McCowan James Duncan
Published: May 2006

N.m.r. spectra obtained preliminary to studies of compounds of the form Cp2TiRCl and Cp2TiR2 raise questions about some previous interpretations of related spectra.
Dielectric Relaxation and Intramolecular Rotation in Aliphatic Ketones
Authors: Crossley John
Published: May 2006

Dielectric constants and losses have been obtained for a number of aliphatic and aromatic ketones in cycloexane, n-hexadecane, decalin and paraffin oil – cyclohexane mixtures at up to ten frequencies between 1 and 145 GHz at 25 °C. Static dielectric constants have also been measured at 2 MHz. The results for each system have been analyzed in terms of a Cole–Cole distribution. The relaxation times and their viscosity dependence are discussed in terms of dipole reorientation by intramolecular and whole molecule rotations.
1:2 Trimethylphosphine Complexes of the Group IV Tetrahalides, trans-MX4•2P(CH3)3 and trans-MX4•2P(CD3)3 (where M = Si, Ge, or Sn; X = Cl or Br); Assignment of Metal–Phosphorus modes
Authors: Frieson D. K. , Ozin G. A.
Published: May 2006

The vibrational spectra of some 1:2 trimethylphosphine adducts of the group IV tetrahalides, which contain ligands in a trans configuration, are examined in detail using perdeutero-trimethylphosphine to facilitate the assignment of all metal–halogen and metal–phosphorus stretching modes. Preparation of SiCl4•2PMe3 with a 1:1 mixture of P(CH3)3 and P(CD3)3 enables an almost unambiguous assignment of the spectrum of this adduct. Normal coordinate calculations for all adducts are reported.
The Direct Observation of a Stereospecific Pentadienyl – Cyclopentenyl Cation Cyclization
Authors: Chiu N. W. K. , Sorensen T. S.
Published: May 2006

Two isomeric 1,2,4,5-tetramethylpentadienyl cations (4a and 4b) have been observed in FSO3H–SO2ClF at −125°. They undergo stereospecific thermal cyclizations to cyclopentenyl cations in accord with the Woodward–Hoffmann rules.
Photoisomerization of Acylsilanes to Siloxycarbenes, and Their Reactions with Polar Reagents
Authors: Duff J. M. , Brook A. G.
Published: May 2006

The photolysis of acylsilanes in a variety of polar reagents (alcohols, acetic acid, HCN, pyrrole, etc.) is shown to involve formation of isomeric siloxycarbenes which act as nucleophiles and insert into the polar H—X bonds present in the reagents. With alcohols as solvents, mixed acetals of an aldehyde with 1 mol each of silanol and alcohol are formed, but these subsequently undergo dark, acid-catalyzed reactions, by one of two mechanisms which involve either carbon–oxygen or silicon–oxygen bond cleavage. The acid catalyst appears to be a by-product of the photolysis reaction. Kinetic and stereochemical evidence is presented in support of the proposed reaction pathways.
Etude du succinate de chrome(II) dihydraté, [Cr(C4H4O4)•H2O]2•2H2O
Authors: Sharrock Patrick , Théophanides Théophile , Brisse François
Published: May 2006

Chromium(II) succinate dihydrate [Cr(II)(C4H4O4)•H2O]2•2H2O has been synthesized for the first time. It has been characterized by its infrared spectrum and by X-ray diffraction. The triclinic unit cell has for dimensions: a = 6.522(10), b = 7.596(3), c = 8.154(4) Å, α = 103.2(1), β = 73.4(1), and γ = 98.7(1)°. This salt is isostructural with copper(II) succinate dihydrate. The red chromium(II) succinate is quickly oxidized in air and the blue oxidation product has composition Cr(III)(C4H4O4)(OH)•H2O.
An Investigation into σ and π Contributions to Long Range 1H–1H Coupling Constants in Conjugated Dienes and Diynes Using CNDO and INDO Molecular Orbital Calculations
Authors: Peat Ian R. , Reynolds William F.
Published: May 2006

Molecular orbital calculations based on finite perturbation theory in the CNDO/2 and INDO approximations are carried out for fourteen conjugated dienes and diynes for which experimental results are available. There is generally very good agreement between experimental and calculated (INDO) coupling constants. Comparison of results of CNDO/2 and INDO calculations elucidates the relative importance of σ and π pathways for the various long-range coupling constants.
Mass Spectral Studies of Binuclear Metal Complexes: Copper(I) Carboxylates
Authors: Lin Denis C. K. , Westmore John B.
Published: May 2006

The thermal decomposition of twenty-five cupric carboxylates was studied by mass spectrometry. In eleven cases volatile cuprous carboxylates (many of which have not been previously reported) were detected amongst the decomposition products. The cuprous carboxylates from acetic, propionic, n-butyric, isobutyric, difluoroacetic, trifluoroacetic, benzoic, p-fluorobenzoic, p-chlorobenzoic, o-chlorobenzoic, and pentafluorobenzoic acids were all found to be dimeric in the vapor phase. Two basically different fragmentation pathways can be proposed depending upon whether the copper salt is formed from an alkyl- or aryl-carboxylic acid. For the former, the spectra are dominated by even-electron fragment ions formed by initial loss of RCO2•from the molecular ion. For the latter, a parallel fragmentation pathway initiated by loss of CO2 from the molecular ion and migration of the aryl group to the metal is also present.
Structure cristalline et moléculaire du cyclopentadiényle dicarbonyle triphénylphosphine manganèse, MnC5H5(CO)2P(C6H5)3
Authors: Barbeau Claude , Dichmann Klaus Sorrento , Ricard Louis
Published: May 2006

The crystalano molecular structure of cyclopentadienyl manganese dicarbonyl-triphenyl phosphine has been determined by means of three dimensional data obtained by a Buerger precession camera. 2931 independent intensities were utilized in the refinement of the structure using the least-squares method. The final disagreement factor is 0.11. MnC5H5(CO)2P(C6H5)3 crystallizes in the triclinic space group.[Formula: see text]The molecule shows atomic parameter almost identical to those of MnC5H5(CO)3 except for the Mn—C bond lengths which change from 1.80 to 1.73 Å. The Mn—P distance (2.236 Å) and the unchanged parameters for the Mn—C5H5 group confirm the strong donating power of the cyclopentadienyl group. [Journal translation]
The Geometrical Dependence of Experimental and Theoretical Nuclear Spin–Spin Coupling Constants in the 15NH2 Fragment
Authors: Wasylishen Roderick E. , Schaefer T.
Published: May 2006

Approximate molecular orbital theory at the INDO level of approximation has been used to examine 1J(15N,H) and 2(HNH) in ammonia as a function of the HNH angle. The couplings are very sensitive to the value of the HNH angle in the range from 110 to 120°. The computed trends are compared with those observed in other compounds containing the 15NH2 fragment. The signs and magnitudes of 1J(15N,H) and 2J(HNH) have been measured for 2-aminoacetophenone at temperatures where the amino protons are nonequivalent. The observed and calculated results suggest that the amino group lies in the plane of the benzene ring. In aniline the magnitude of 2J(HNH) lies between 1 and 2 Hz and on the basis of the trends in the calculated and experimental values the sign can be confidently taken as negative.
Synthetic Approaches to a Novel Carbohydrate Conjugated Diene: 4,6-O-Benzylidene-1,2,3-trideoxy-3-C-methylene-D-erytho-hex-1-enopyranose
Authors: Tam Steve Y-K. , Iley David E. , Holder Neville L. , Hicks David R. , Fraser-Reid Bert
Published: May 2006

Four routes to the title compound 1 are outlined, three of which (i), (ii), and (iv) are simple one-step processes from readily available carbohydrate precursors. In the third route (iii) the α-keto benzoate 6a is methylenated and the benzoate group replaced by methanesulfonate. The product (6d) rearranges upon iodinolysis giving the primary allylic iodide (2b) which undergoes 1,4-elimination with methyl lithium to give the title compound (1). All reaction intermediates are readily crystallizable and with the exception of (6b) obtainable in > 80% yield.
Nucleic Acid Related Compounds. 8. Direct Conversion of 2′-Deoxyinosine to 6-Chloropurine 2′-Deoxyriboside and Selected 6-Substituted Deoxynucleosides and Their Evaluation As Substrates of Adenosine Deaminase
Authors: Robins Morris J. , Basom Gerald L.
Published: May 2006

Trifluoroacetylation of 2′-deoxyinosine (2), obtained by enzymatic deamination of 2′-deoxyadenosine (1), gave the 3′,5′-bis-O-trifluoroacetate (3). Reaction of the electronegatively substituted deoxynucleoside, 3, with DMF-thionyl chloride complex in refluxing methylene chloride gave a high yield of 6-chloropurine 2′-deoxyriboside (4) after deblocking.Displacement of chloride of 4 by hydrosulfide to give 6-mercaptopurine 2′-deoxyriboside (5) followed by sulfur alkylation with p-nitrobenzyl bromide gave 6-S-(p-nitrobenzyl) thiopurine 2′-deoxyriboside (6) which was alternatively prepared by displacement of chloride from 4 by p-nitrobenzyl mercaptide, generated in situ from the isothiouronium salt. Methyl mercaptide reaction with 4 gave 6-methylthiopurine 2′-deoxyriboside (7). Treatment of 4 with trimethylamine gave the corresponding quaternary ammonium chloride (8) which was allowed to react with potassium fluoride to give 6-fluoropurine 2′-deoxyriboside (9). Respective amine displacements on 4 gave 6-benzylaminopurine 2'-deoxyriboside (10), and 6-hydroxylaminopurine 2′-deoxyriboside (11). Reaction of 4 with liquid ammonia completed the first reported transformation of 2′-deoxyinosine (2) to 2′-deoxyadenosine (1).Biological rationale for the synthesis of these 2′-deoxynucleosides and their evaluation as substrates of adenosine deaminase are discussed. Major mass spectral fragmentations are tabulated.
Nuclear Magnetic Resonance Experiments on Acetals. 43. Reversal of Previous Conformational Assignment in 5-Fluoromethylated-5′-Me-1,3-dioxanes
Authors: Anteunis M. , Borremans F.
Published: May 2006

Additional n.m.r. investigations on 5-fluoromethylated-5′-Me-1,3-dioxanes have made it necessary for us to reverse the spectral assignments which were forwarded recently (1) in this journal. Thus, the 5-CF2H group prefers the axial position to the extent of ca. 900 cal/mol, whereas the 5-CFH2 group displays a similar preference for the axial position to the extent of ca. 200 cal/mol. An explanation for these unexpected results is advanced. Final structural assignments have been made possible by homo- and heteronuclear double resonance experiments and by ASIS-studies. The observed relative shifts for 5-CFnH3−n and 5-CH3 signals are shown to be normal (e.g. δ(5e) < δ(5a)). Also, the previously reported 4J(F,H) long range couplings follow a classical M-path.
Gas–Liquid Chromatography – Mass Spectrometry of Permethylated Aldosyl Aldonates
Authors: Whyte John N. C.
Published: May 2006

Oxidation of neutral disaccharides yielded aldosyl aldonic acids which were methylated and separated by g.l.c. and subjected to mass spectrometry. The electron-impact fragmentation patterns afforded by these derivatives discriminated between (1 → 3), (1 → 4), and (1 → 6) linked residues and differed from that postulated for (1 → 2) intermolecular bonds. Primary scission of the aldonate moieties provided for the ionized hexosyl containing fragments which formed the high mass diagnostic peaks in these spectra. The mass spectra exhibited by the oxidized products could be correlated to those obtained from reduced, permethylated pseudoaldobiouronic acids.