bluuebunny/crossref_metadata_2025 huggingface dataset:
Isotope effect studies on elimination reactions. VI. The mechanism of the bimolecular elimination reaction of 2-arylethylammonium ions
Authors: Smith P. J. , Bourns A. N.
Published: May 2006

The mechanism of the elimination reaction of 2-arylethyltrimethylammonium ions with ethoxide ion in ethanol has been examined using tracer and kinetic isotope effect techniques. Absence of exchange with solvent of both 2-phenylethyltrimethylammonium-2,2-d2 bromide and 2-(p-trifluoromethylphenyl)-ethyltrimethylammonium-2,2-d2 bromide and the observation of nitrogen isotope effects of 1.3 and 0.9%, respectively, have eliminated a two-step process involving a freely-solvated carbanion intermediate for both salts. The observation of only a slight change in the magnitude of the nitrogen isotope effect when the solvent is changed from ethanol to water has also excluded a zwitterionic intermediate which is specifically hydrogen-bonded to the molecule of ethanol formed by removal of a β-hydrogen by ethoxide ion. Finally, tracer studies using α- and β-dideuterated substrates have eliminated the less probable reaction pathways involving ylide and carbene intermediates. It is concluded that the reaction of 2-arylethyltrimethylammonium salts with ethoxide ion is a concerted E2 process.
Volume changes in electrolytic hydrogen evolution at mercury in aqueous hydrochloric acid
Authors: Smith Frank R. , Heintze Hans-Ulrich
Published: May 2006

Volume changes at a mercury cathode in hydrogen-saturated aqueous 0.1 M hydrochloric acid during electrolysis at 25 °C are less than those predicted by Faraday's Law[Formula: see text]over a range of current densities from 0.4 to 83 μA mm−2. Difficulties attributable to the anodic reaction of mercury were found using an apparatus similar to that of Müller (1) but constructed entirely of glass. A two-compartment cell proved to be advantageous in isolating the cathode reaction. Rates of volume change attributable to formation of H2(g) almost invariably increased with time of electrolysis but were always below expectation. In agreement with Müller, an increase of volume was observed after electrolysis. The evidence is consistent with formation and subsequent decomposition of a hydrogen amalgam. It suggests that, contrary to the usual assumptions (2), hydronium-ion discharge is not the slowest step in the overall hydrogen gas-producing reaction.
Studies in isoxazole chemistry. II. Isoxazoles from the Δ2-isoxazolin-5-ols and their acetates
Authors: Micetich R. G.
Published: May 2006

Various 3-substituted-5-acetoxy-Δ2-isoxazolines were made by the 1,3-dipolar cycloaddition of nitrile oxides to vinyl acetate or isopropenyl acetate. These compounds were readily converted in high yield to 3-substituted isoxazoles or 3-substituted-5-methylisoxazoles respectively, on heating. Treatment of the 3-substituted-5-acetoxy-Δ2-isoxazolines with sodium hydroxide in methanol gave rise to the stable Δ2-isoxazolin-5-ols after acidification. These compounds could also be converted to 3-substituted isoxazoles by heating alone, or better, in the presence of thionyl chloride. The nuclear magnetic resonance spectra of these compounds are discussed.
Electron spin resonance study of trapped electrons in irradiated organic glasses at 4.2 °K
Authors: Yoshida Hiroshi , Higashimura Takenobu
Published: May 2006

Electron spin resonance of electrons trapped in organic glasses, ethanol, 2-methyltetrahydrofuran, and 3-methylhexane were studied at the four different conditions (combination of irradiation with γ-rays and measurement at both 77 and 4.2 °K). It was evident that the spectral width, ΔHms, changes irreversibly when the glasses are warmed up to 77 °K after the irradiation at 4.2 °K: from 6.7, 5.6, and 4.5 to 14, 4.4, and 4.0 G for ethanol, 2-methyltetrahydrofuran, and 3-methylhexane, respectively. These observations strongly support Smith and Pieroni′s (4) suggestion that the molecular orientation is not a necessary condition for electrons to be trapped in the irradiated organic glasses.
Cumulative yields in the photofission of 232Th and 238U in the symmetric region
Authors: Gevaert L. H. , Jervis R. E. , Subbarao S. C. , Sharma H. D.
Published: May 2006

Fission mass yields for molybdenum-99, ruthenium-103 and -105, palladium-109 and -112, silver-111, cadmium-115, and tin-121 and -125 in the 25 MeV bremsstrahlung beam fission of thorium-232 and uranium-238 have been determined using radiochemical methods. The mass–yield curve for thorium-232 shows a pronounced third peak in the symmetric region, contrary to the results of Hiller and Martin with 69 MeV brehmsstrahlung. In the case of uranium-238, the curve is flat between mass numbers 111 to 121 in contrast to the 14 MeV neutron fission of the nuclide which shows a valley in this region.
Detection and chemistry of the triplet state of thymine
Authors: Szabo A. G. , Rlddell W. D. , Yip R. W.
Published: May 2006

The transient produced on flash excitation of degassed solutions of thymine in acetonitrile has been characterized as the triplet excited state of thymine. This triplet state has a lifetime of 14 ± 1 μs and the associated dimerization rate was found to be 5.3 ± 0.3 × 108 M−1 s−1. The triplet state of thymine could be quenched by 2,4-hexadien-1-ol with a rate constant of 8.1 ± 0.6 × 109 M−1 s−1.
Methyltin trinitrate and a comparison of its properties with other methyltin nitrates
Authors: Ferraro J. R. , Potts D. , Walker A.
Published: May 2006

Methyltin trinitrate has been prepared by the reaction of dinitrogen pentoxide on methyltin trichloride in carbon tetrachloride, followed by sublimation in vacuo at 60 °C. Conductivities and ultraviolet spectra of methyltin trinitrate in several solvents are reported. Vibrational spectra indicate that the three nitrato groups are all bonded in the same bidentate manner and the reactivity of the compound towards aliphatic hydrocarbons and diethyl ether shows that the compound is chemically similar to tin(IV) nitrate. The vibrational spectrum of methyltin trinitrate is compared with those for trimethyltin nitrate, dimethyltin dinitrate, and tin(IV) nitrate. Nuclear magnetic resonance spectra have been determined for the series MenSn(NO3)4−n (n = 1,…, 4), and a comparison of the 117Sn– and 119Sn–proton coupling constants for the series has been made showing that the tin atom becomes more electron deficient and has more s character in its bonding orbital to carbon as n decreases. The pyridine adduct MeSn(NO3)3•2py has been prepared and the infrared spectrum of this compound indicates that the nitrate groups are unidentate.
Decomposition of aqueous dithionite. Part I. Kinetics of decomposition of aqueous sodium dithionite
Authors: Lem W. J. , Wayman M.
Published: May 2006

A rate equation for the total path of decomposition of aqueous Na2S2O4 in the pH range 3.5–5.0 at 23 °C was determined, taking into account the rapid autocatalytic decomposition as well as the "induction" period. The kinetic data were determined by a continuous polarographic method. The form of the rate equation was found by studying the decomposition of aqueous Na2S2O4 at various values of pH and at various initial concentrations. Rate constants were calculated from the data using the integrated form of the rate equation. The rate equation, with certain limitations, was found to be[Formula: see text]Where k1 = 1.67 × 10−1 l mole−1 s−1 and k2 = 5.83 × 103 l2 mole−2 s−1 at 23 °C; C and C0 being dithionite concentration at time t and initial concentration, respectively. The integrated form of the rate equation was used to generate decomposition curves, which are in reasonable agreement with the experimental data.
The Hg 6(3P1) photosensitized decomposition of methyl vinyl ether
Authors: Morris R. V. , Filseth S. V.
Published: May 2006

The mercury 6(3P1) photosensitized decomposition of methyl vinyl ether has been studied in the vapor phase in a static system at 55 °C between 0.2 and 10.0 Torr. The principal products are propanal and ethane. It is concluded that the primary process involves the direct production of methyl and vinoxy radicals with no more than 3% participation of a competing step producing ethylene. Neither carbon–hydrogen bond breaking nor the production of primary excited molecules is observed.
Tetrahydropyranyl protecting group. II. 3-Bromo-2-(tetrahydropyran-2-yloxy)propene, a masked acetonyl bromide
Authors: Horning D. E. , Kavadias G. , Muchowski J. M.
Published: May 2006

It is shown that the sodium hydride (in dimethyl formamide) induced elimination of hydrogen bromide from 1,3-dibromo-2-(tetrahydropyran-2-yloxy)propane (3) can be considered to result in the in situ formation of 3-bromo-2-(tetrahydropyran-2-yloxy)propene (4). When generated in this manner, 4 was shown to function as a masked acetonyl bromide of considerable utility. Under similar conditions, 1,3-dibromo-2-methoxypropane was assumed to produce 3-bromo-2-methoxypropene, which also was shown to be a useful masked acetonyl bromide.The pyrolytic elimination of methanol from bromoacetone dimethyl ketal was shown to produce a 1:1 mixture of the two possible isomeric enol ethers, rather than pure 3-bromo-2-methoxypropene as stated in the literature (2).
Crystalline-field effects on the infrared and Raman spectra of powdered alkali-metal, silver, and thallous nitrates
Authors: Brooker M. H. , Irish D. E.
Published: May 2006

Infrared and Raman spectra have been recorded for room-temperature-phase, powdered samples of LiNO3, NaNO3, KNO3, RbNO3, CsNO3, AgNO3, and TlNO3. For the trigonal systems, the nitrate pairs LiNO3, NaNO3 and RbNO3, CsNO3 give almost identical spectra. For the orthorhombic systems, AgNO3 and TlNO3 give similar spectra, whereas that of KNO3 is significantly different. Site and correlation field perturbations are considerably more pronounced in the antisymmetric stretching region (ν3 ca. 1400 cm−1) than in the antisymmetric bending region (ν4 ca. 700 cm−1). Although lifting of the degeneracy of E′ modes was frequently observed, the reported split of the ν4(E′) mode (ca. 716 cm−1) of the aragonite form of KNO3 could not be confirmed. Multiple internal reflectance techniques have been employed to observe the extremely intense ν3(E′) infrared fundamental ca. 1400 cm−1.
Lemon-peel pectin. II. Isolation of homogeneous pectins and examination of some associated polysaccharides
Authors: Aspinall G. O. , Cottrell I. W.
Published: May 2006

Two electrophoretically homogeneous pectins have been isolated from dried lemon-peel under conditions of minimum degradation by extraction with cold water and with disodium ethylenediaminetetraacetate. Some properties of polysaccharides which occur in association with the pectins are reported.
Activities and ionic distributions in liquid silicates: application of polymer theory
Authors: Masson C. R. , Smith I. B. , Whiteway S. G.
Published: May 2006

Theoretical expressions derived previously for molecular size distributions in multichain polymers are applied to binary silicate melts. The treatment is an extension of a previous approach which was limited to the consideration of linear chains. When all configurations of the chain molecules are taken into consideration, the predicted variation of thermodynamic activity with composition agrees with experiment for all binary systems for which data are available. The effect of allowing for all chain configurations is largely to improve the fit between theory and experiment at high silica contents. Calculated ionic distributions for the system 'FeO'–SiO2 do not differ markedly from those previously reported. The mean chain length is unaffected. The results support previous views that principles of polymer chemistry can be applied usefully to silicate melts and glasses.
Electron spin resonance studies of radiation damage. Part III. Gamma irradiated acetonitrile
Authors: Sargent F. P.
Published: May 2006

The effects of photobleaching and thermal decay at 77 and 87 °K on the electron spin resonance spectra of gamma irradiated acetonitrile are reported.
A quantum-chemical study of some properties and reactions of H2CN−, H2CN+, H2CNH2+, H2CNH, and HCN, using small and intermediate-sized sets of basis functions
Authors: Moffat J. B.
Published: May 2006

It is suggested that given two molecules potentially capable of being involved in the same reaction, one as a product and one as a reactant, it seems reasonable that the calculated difference in energy between these molecules may become relatively constant with smaller basis sets than the calculated energies themselves. To examine this suggestion, and at the same time to provide information on small molecules containing bonds related to the nitrile bond, a number of linear combination of atomic orbitals-molecular orbitals-self consistent field (l.c.a.o.-m.o.-s.c.f.) calculations using small or intermediate sizes of basis sets of Gaussian orbitals were performed on H2CNH, H2CN−, H2CNH2+, H2CN+, and HCN. The change of energy in passing from one molecule to another is shown to converge to a reasonably constant value for smaller basis sets than are required for convergence of individual molecular energies.
Reaction of bis(trifluoromethyl)diazomethane with trimethyl-3,3,3-trifluoropropynyltin, trimethyltin hydride, and related compounds
Authors: Cullen W. R. , Waldman M. C.
Published: May 2006

Bis(trifluoromethyl)diazomethane (1) reacts with the compounds (CH3)3MC≡CCF3 (M = Ge, Sn) to give the cyclopropenes [Formula: see text]. Cyclopropenes are also obtained from the reaction of 1 with the acetylenes RC≡CCF3 (R = H, CF3) but the main products are the isopyrazoles [Formula: see text]. Compound 1 reacts easily with (CH3)3SnH to give (CH3)3SnC(CF3)2H and a similar insertion reaction takes place with (CH3)2AsH. Compound 1 does not insert into Si—H, Ge—H, Ge—Br, Ge—Ge bonds. It reacts with (CH3)2As—As(CH3)2 to give (CH3)2AsC(CF3)2H. Bis(trifluoromethyl)diazirine also reacts with (CH3)3GeC≡CCF3 to give the cycldpropene.
Nuclear charge dispersion of light-mass fission products in the fission of 235U and 238U by medium-energy protons
Authors: Khan A. H. , Saha G. B. , Yaffe L.
Published: May 2006

Independent fission yields for 90Ym, 90Ym+g, 91Ym, 91Ym+g, and 92Y and cumulative yields for 91Sr, 92Sr, and 93Y in the fission of 235U and 238U by protons of energy from 20–85 MeV have been determined. Excitation functions and charge dispersion curves have been obtained. The most probable charge, Zp, moves closer to stability, ZA, with increasing energy. The values of ZA − Zp for the two fissioning systems are identical, unlike the situation in the heavy-mass region. The values of ZA − Zp for the light- and heavy-mass regions differ considerably, showing that the equal charge displacement hypothesis does not hold even at these moderate energies.
Effect of pressure on the solvolysis of benzyl chloride in glycerol–water mixtures
Authors: Gay D. L. , Whalley E.
Published: May 2006

The effect of pressure up to 1.6 kbar on the rate of solvolysis of benzyl chloride in 0 to 75% v/v glycerol–water has been measured at 50 °C. The volume of activation is −10.7 ± ~ 0.4 cm3 mole−1, essentially independent of solvent composition. Therefore, the partial volumes of both benzyl chloride and the transition state depend on solvent composition in the same way. The constant-volume energy and entropy of activation are simple functions of the solvent composition, and resemble the constant-volume parameters in ethanol–water mixtures. It is concluded that constant-volume conditions are probably more appropriate than constant-pressure conditions for discussing the solvent dependence of these solvolyses.
Substituent effects on geminal proton–proton coupling constants
Authors: Chow Y. L. , Black S. , Blier J. E. , Tracey M. M.
Published: May 2006

The geminal coupling constants between the non-equivalent benzylic protons of a series of para- and meta-substituted N-benzyl-2-methylpiperidines were shown to be proportional to the Hammett σ constants of the substituents with ρ −1.38 in carbon tetrachloride, −1.21 in benzene, and nearly 0 in 1 N DCl solutions. The ρ values were compared with those of other series and were discussed in terms of the possible conformations involved. The chemical shifts of the benzylic protons of the piperidine derivatives did not give a good correlation with the Hammett σ constants in these solvents.
Selective removal of phenolic groups in certain dihydroxytoluenes by tetrazole ether formation and hydrogenolysis
Authors: Barfknecht C. F. , Smith R. V. , Reif V. D.
Published: May 2006

Selectivity and yield were studied in the reaction of 5-chloro-1-phenyltetrazole with dihydroxytoluene systems. The mono-ethers of 2-methylhydroquinone (1a), 3-methylcatechol (2a), and 4-methylcatechol (3a) were formed in moderate yields with the predominant isomer resulting from attack by the more nucleophilic anion. With 1a and 2a, steric effects diminished the amount of predominant isomer formed as compared to 3a. The di-(1-phenyltetrazole) ethers were formed in good yields. Hydrogenolysis of mono- and di-ethers gave good yields of cresols and toluene as determined by gas chromatography and ultraviolet analysis, respectively.
1,3-Dipolar cycloaddition of nitrosonaphthols to 3-aroylazindines. Novel syntheses of substituted naphtho[1,2-d]oxazoles and naphtho[2,1-d]oxazoles
Authors: Lown J. W. , Moser J. P.
Published: May 2006

A series of 3-aroyl-2-arylaziridines underwent 1,3-dipolar cycloadditions in both orientations to the nitrogen–oxygen bond of 1-nitroso-2-naphthol. Spontaneous 1,3-cleavage of the intermediate oxadiazolidines to nitrones and cyclodehydration of the latter afforded both 2-aryl- and 2-aroylnaphtho-[1,2-d]oxazoles in good yields. The interpretation of the reaction received confirmation by independent, unambiguous synthesis of several 2-aroylnaphtho[1,2-d]oxazoles.
The photolysis of azomethane in the presence of HN3
Authors: Konar R. S. , Darwent B. deB.
Published: May 2006

The photolysis of azomethane by 3660 Å light at 25 °C, has been used as the source of CH3 to investigate their reactions with HN3. CH3 reacts rapidly with HN3 to produce CH4 with k = 8.9 × 104 M−1 s−1. The addition of CH3 to the double bonds in HN3 is much slower. The mechanism by which N3 radicals disappear has been discussed.
The use of Raman spectroscopy in the study of anion exchange of complex anions
Authors: Dobud P. , Sutton D. , Tuck D. G.
Published: May 2006

It is shown that Raman spectroscopy can be used to identify complex anions sorbed on an anion exchange resin. Results for [AuCl4]− and [AuBr4]−, and for anionic halo-complexes of indium(III), are described.
The ethenoxy radical in the pyrolysis of acetaldehyde
Authors: Schuchmann H.-P. , Laidler K. J.
Published: May 2006

In the pyrolysis of pure acetaldehyde at 450–525 °C it was found that ketene, although stable under these conditions, is not formed as a final reaction product. This result requires a modification of the mechanism of Liu and Laidler, according to whom the ethenoxy radical CH2CHO splits into CH2CO and H. It is concluded that instead of splitting unimolecularly, CH2CHO disappears mainly through the reaction[Formula: see text]and that it also undergoes the process[Formula: see text]
The isothermal compressibility of dimethylsulfoxide–water mixtures at 35 °C
Authors: Jung K. H. , Hyne J. B.
Published: May 2006

The isothermal compressibility of a series of dimethylsulfoxide–water mixtures passes through a minimum near 0.4 mole fraction dimethylsulfoxide. This behavior is compared with that of other aqueous binaries and provides further evidence of specific hydrogen bonded complexes in the dimethylsulfoxide–water system.
Etude de la cycloalcoylation des (thiényl-2)-5 pentènes-1
Authors: Gourier J. , Canonne P.
Published: May 2006

Cyclizations of 5(2-thienyl)pent-1-enes substituted at carbon-4 (COOH, COOCH3, CH2OH, or CH3) by the action of mineral and Lewis acids are reported. The yield of cyclized product varies with the nature of the substituent, the acid catalyst employed, and the reaction time.
Surface tension of some non-aqueous salt solutions
Authors: Stairs R. A. , Rispin W. T. , Makhija R. C.
Published: May 2006

The surface tensions of methanol, acetone, dimethylformamide, dimethylsulfoxide, and methylamine over limited temperature ranges, and of solutions of alkali halides in the first three of these liquids at 25 °C have been measured by the method of maximum bubble pressure, with precautions against moisture. The data for the pure liquids are compared with literature data where these exist. The results for the solutions are discussed in the light of various existing theories.
Etude par résonance magnétique nucléaire à température variable de composés apparentés au méthylènecyclohexane
Authors: Bernard Michel , St-Jacques Maurice
Published: May 2006

Spectral modifications have been observed in the n.m.r. spectra of difluoromethylenecyclohexane, isopropylidenecyclohexane, and dichloromethylenecyclohexane. The free energy barriers for conformational interconversion in these compounds have been estimated and are discussed.
The pyrolysis of trimethylarsine
Authors: Price S. J. W. , Richard J. P.
Published: May 2006

The pyrolysis of trimethylarsine has been studied in a toluene carrier flow system from 764 to 858 °K using total pressures from 6.35 to 35.5 mm. Contact times varied from 0.9 to 3.7 s and the amount of decomposition, from 1.2 to 73 %. The progress of the reaction was followed by measuring the amount of methane, ethane, ethylene, and ethylbenzene formed. No heterogeneous reaction was detected and the first order rate constants appear to have been determined at approximately the high pressure limit. In seven runs the undecomposed alkyl was also measured. The quantity found was in agreement with the product analysis if three methyl radicals are released for each molecule undergoing reaction.Least squares analysis of the results gives[Formula: see text]The activation energy should be a good approximation to D[(CH3)2As—CH3]. The product analysis and the values of k4/k51/2 are consistent with the simple consecutive release of three methyl radicals but thermodynamic and kinetic considerations may preclude this possibility.
Mechanism of decarboxylation of substituted anthranilic acids at high acidity
Authors: Dunn G. E. , Dayal S. K.
Published: May 2006

The rates of decarboxylation of 4-methyl-, 4-methoxy-, and unsubstituted anthranilic acids have been determined in aqueous buffers over the pH range 2.5–3.8. Electron-releasing substituents increase the rates of ring-protonation about equally for an acid and its anion, and decrease the ratio of decarboxylation to deprotonation of the protonated acid. Rates, 13C-carboxyl kinetic isotope effects, and deuterium solvent isotope effects have been determined for the decarboxylation of anthranilic acid in aqueous sulfuric acid up to 10 M. No evidence for decarboxylation by cleavage of the unionized carboxyl group was obtained.
The 19F nuclear magnetic resonance spectra of antimony pentafluoride, cis-Sb3F16− and higher polyanions SbnF5n+1−
Authors: Bacon J. , Dean P. A. W. , Gillespie R. J.
Published: May 2006

The resonances in the 19F nuclear magnetic resonance (n.m.r.), spectrum of antimony pentafluoride have been reassigned and it is shown that the fine structure observed in the spectrum of antimony pentafluoride in various inert solvents can only be explained by considering the effects of magnetic nonequivalence. Solutions of t-butyl fluoride and tetra-n-butylammonium hexafluoroantimonate in excess SbF5/SO2ClF are shown to contain the Sb3F16− and Sb4F21− anions which have cis-fluorine bridged structures. The coupling constants and chemical shifts in the n.m.r. spectra of Sb3F16−, Sb4F21−, (SbF5)n and 1:1 and 2:1 complexes of SbF5 are compared and discussed.
Stabilities of nickel–alkyl compounds
Authors: Thomson J. , Baird M. C.
Published: May 2006

The compounds π-C5H5Ni(PPh3)R (R = Me, Et, n-Pr, iso-Pr, n-Bu, sec-Bu, iso-Bu) have been prepared and characterized. Thermal decomposition of these compounds in xylene solution yields, in all cases except the methyl, an olefin and an olefin isomerization catalyst.
Multiple resonance n.m.r. study of 2α-fluoro-cholestan-3-one
Authors: Grant C. W. M. , Hall L. D.
Published: May 2006

A detailed n.m.r. study has been made of 2α-fluoro-cholestan-3-one, with particular emphasis on the parameters of the nuclei attached to ring A. This study illustrates the potential of 1H–{1H}and 19F–{1H} heteronuclear decoupling experiments and of the 1H–{1H} INDOR technique as adjuncts to n.m.r. studies of fluorinated, and other, steroid derivatives.
The kinetics and mechanism of the reactions between carbon monoxide and ruthenium(II) chlorides in solution
Authors: Hui B. C. , James B. R.
Published: May 2006

The kinetics of formation of mono- and dicarbonyl complexes in two successive stages by direct carbonylation of ruthenium(II) chlorides in dimethylacetamide solution have been studied at 65–80° and up to 1 atm CO by gas uptake techniques. Both stages are first order in ruthenium. Formation of the monocarbonyl is independent of CO pressure; dicarbonyl formation is first order in CO at low pressures with the order decreasing towards zero with increasing pressure, and shows an inverse chloride dependence from 0.1–2.0 M added chloride. For both stages, the data are consistent with a mechanism involving predissociation. A similar mechanism is suggested for the corresponding reactions in 3 M HCl solution which had been studied earlier and which showed overall second-order kinetics.Discussion on the related formation of molecular nitrogen complexes of ruthenium(II) is presented.
Preparation and characterization of some α,α-disubstituted-α-hydroxythiolesters
Authors: Elias Wilma E.
Published: May 2006

A series of α,α-disubstituted-α-hydroxythiolesters has been prepared from ketone cyanohydrins by the Pinner reaction. The esters have been characterized both by classical methods and by analysis of their i.r. n.m.r., and u.v. spectra.
Simple and quick method for the dielectric study of solid powders
Authors: Srivastava K. K. , Wright G. F , Khanna S. L. , Krishan Iqbal , Nayar R. K.
Published: May 2006

The dielectric constant values for many substances have been determined at a frequency of 1 MHz by the method discussed in the paper. In some cases, these values have also been determined by other commonly used methods and show a good agreement.
Acylation of 2-methyl-2-thiazoline
Authors: Durst T. , Manoir J. Du
Published: May 2006

The acylation of 2-methyl-2-thiazoline initially reported by Sheehan etal. (1) has been reinvestigated and reinterpreted. The initially formed 2-chloro-N-acylthiazolidine (e.g. 8) can be dehydrohalogenated to a 2-methylene-N-acylthiazolidine by reaction with triethylamine or converted to a 2-hydroxy-N-acylthiazolidine on addition of water. Contrary to the earlier report no 2-methyl-N-acyl-4-thiazolines are produced when the reaction is carried out in benzene at 60° and in the presence of excess triethylamine.
Donor–acceptor interactions in Friedel–Crafts systems. The CH3COCl•AlCl3 addition compound
Authors: Cassimatis D. , Bonnin J. P. , Theophanides T.
Published: May 2006

The infrared spectra of CH3COCl and CH3COCl•AlCl3 have been studied from 4000 to 300 cm−1 with a Perkin–Elmer 621 grating spectrophotometer. The results indicate that the addition compound CH3COCl•AlCl3 exists under three structures, two ionic and one dative structure. The distinct ionic structures are the carbonium type structure [Formula: see text] with a carbonyl band at 2200 cm−1 (type 1) and a structure visualized as a hybrid between resonating structures[Formula: see text]where the mesomeric limit form corresponding to the hyperconjugation is preponderant, with a carbonyl band at 2300 cm−1 (type 2). Vibrational assignments have been made for the two ions and supported by normal coordinate analysis. Two sets of force constants have been derived on the basis of the generalized force field for the two ionic structures to provide a correspondence between observed and calculated frequencies. Evidence would seem to show that the active species in the Friedel–Crafts ketone synthesis is the oxocarbonium type 1 acetylium ion.
Synthesis of vitamin K1 analogs. A new class of vitamin K1 antagonists
Authors: Lowenthal J. , Chowdhury M. N. Roy
Published: May 2006

The synthesis of two analogs of vitamin K1, namely, 2-chloro (2) and 2-bromo (3) analogs, is described. The separation of cis and trans isomers of both these compounds on preparative t.l.c. is reported along with the spectral data.
Exchange Reactions of the t-Butyl Cation
Authors: Brownstein S. , Bornais J.
Published: May 2006

The exchange reaction between t-butyl cation and isobutane in sulfur dioxide solution is first order in both species with Ea = 3.6 kcal/mole and ΔS*298 = −27 e.u. No reaction is observed, under these conditions, between the t-butyl cation and n-butane or neopentane. In a similar system the isopropyl chloride – arsenic pentafluoride complex reacts rapidly with n-butane to yield propane and the t-butyl cation, but does not react with neopentane or cyclopropane. An exchange reaction was also observed between the isopropyl chloride – arsenic pentafluoride complex and propane.
Proton Magnetic Resonance Spectrum of Parafluorotoluene. Sigma and Pi Electron Contributions to JpH,F
Authors: Wasylishen R. , Schaefer T.
Published: May 2006

The p.m.r. spectrum of a 15 mole % solution of p-fluorotoluene in acetone-d6 is analyzed at 100 MHz using LAOCN3 and LAME computer programs. The resulting spectral parameters satisfactorily reproduce the methyl proton resonance at 60 MHz. The coupling over six bonds between the fluorine nucleus and the methyl protons is 1.15 ± 0.02 Hz and is taken as a measure of the π electron contribution to the coupling over five bonds between the fluorine nucleus and the proton in p-fluorobenzene. The σ electron contribution to this coupling is discussed for some fluorobenzene derivatives and is shown to depend on the electronegativity of the substituents in a manner completely analogous to proton–proton and other proton–fluorine couplings in benzene and pyridine derivatives.
5,6-Dehydrolupanine, a New Alkaloid, and Lupanine from Thermopsis rhombifolia (Nutt.) Richards
Authors: Cho Y. D. , Martin R. O.
Published: May 2006

In addition to the alkaloids originally reported in flowering plants of T. rhombifolia, lupanine (3) and a new major alkaloid were isolated from 6 week old plants. This new alkaloid has been characterized as 5,6-dehydrolupanine (7).
Oxydation lente du cétène en phase gazeuse. II. Réaction à "basses températures"
Authors: Michaud Pierre , Oueixet Cyrias
Published: May 2006

The slow combustion of ketene was investigated in the low-temperature range 280–350 °C. It differs from the reaction at higher temperatures chiefly by the presence of peroxides (mostly hydroperoxides) and the absence of methane. The main products: formaldehyde, carbon monoxide, water, and carbon dioxide are the same in both cases. A reaction scheme is proposed, which involves degenerate branching through the decomposition of methyl hydroperoxide: CH3OOH = CH3O• + •OH.
Kinetics of the Mercury-Photosensitized Decomposition of Propane. Part II. Reactions of the Propyl Radicals
Authors: Papic M. M. , Laidler K. J.
Published: May 2006

The results of the previous paper are analyzed to yield information about the reactions of the n-propyl and i-propyl radicals. The various combination and disproportionation reactions are considered. The rate of decomposition of the n-propyl radical was determined as a function of temperature and pressure, and limiting high-pressure and low-pressure kinetic parameters were obtained. The high-pressure activation energy is 32.6 kcal mol−1, and this leads to a value of 24.3 kcal mol−1 for the dissociation energy of the C—C bond in the n-propyl radical, to 22.2 kcal mol−1 for its heat of formation, and to 99.1 kcal mol−1 for the primary C—H dissociation energy in propane. Entropy changes are also calculated from the results.For the decomposition of the i-propyl E∞ = 38.7 kcal mol−1, and this leads to 37.7 kcal mol−1 for the C—H bond dissocation energy in this radical and to 19.3 kcal mol−1 for its heat of formation. The secondary C—H dissociation energy in propane is calculated to be 96.2 kcal mol−1. Corresponding entropy changes are calculated.
Conversion of a 3-Oxaquadricyclane to a Substituted Cyclobutane. Preparation and Proton Magnetic Resonance Spectra of Four Stereoisomeric 1,2-Diacetyl-3,4-dicarbomethoxycyclobutanes
Authors: Laing J. , Mcculloch A. W. , Smith D. G. , Mcinnes A. G.
Published: May 2006

Reaction of l,5-dicarbomethoxy-2,4-dimethyl-3-oxaquadricyclane with water gave a mixture of cis,cis,cis- and cis,cis,trans-1,2-diacetyl-3,4-dicarbomethoxycyclobutanes. The latter on treatment with acid epimerized to the corresponding trans,trans,trans-isomer, whereas the former yielded the trans,trans, cis-epimer together with 3,10-dimethyl-3,10-epoxy-5,8-dioxo-4,9-dioxatricyclo[5.3.0.02,6]decane which contains a new bridged ring system. The structure and stereochemistry of each compound was derived from symmetry considerations as reflected in its p.m.r. spectrum, and was facilitated by selective deuteration experiments. Vicinal and long-range spin–spin interactions between the cyclobutane ring hydrogens were deduced from pertinent p.m.r. sub-spectra using the NMRIT–NMREN computer program.
Studies of Carbohydrate Derivatives by Nuclear Magnetic Double Resonance. Part VI. The Identification of 13C Chemical Shifts of Methyl Resonances via the 1H–{13C} INDOR Technique
Authors: Burton R. , Hall L. D. , Steiner P. R.
Published: May 2006

The 13C chemical shifts of acetate- and methoxyl-methyl substituents of several pyranose carbohydrate derivatives have been measured by the 1H–{13C} INDOR technique. The chemical shifts (δ13C) of anomeric methoxyl-methyl resonances fall into two groups: for α-anomers (axial substituent), δ13C = 55.12–56.63 p.p.m.; for β-anomers (equatorial substituent), δ13C = 56.63–8.69 p.p.m. O-Acetyl-methyl shifts fall between 20.54–20.72 p.p.m. and N-acetyl-methyl shifts were detected between 22.98–23.08 p.p.m.
Mechanism of Oxidative Decarboxylation of α-Hydroxy Acids by Bromine Water. Part I. Oxidation in Neutral and Alkaline Medium
Authors: Pink Judith M. , Stewart Ross
Published: May 2006

A kinetic study of the oxidative decarboxylation of α-hydroxy acids by bromine water shows that above pH 6 Br2 is a much more significant oxidant for these compounds than is HOBr, and that OBr− is virtually inert. The rate law – d[oxidant]/dt = k[oxidant][substrate] is observed and the oxidation pattern differs from that of alcohols in that the α-hydrogen is not involved in the reaction.All the compounds studied (benzilic, mandelic, and 2-hydroxy-2-methylpropanoic acids) exhibit bell-shaped pH-rate profiles with maxima at about pH 8. A mechanism is proposed involving the attack of Br2 (or HOBr) at the carboxylate site concurrently with base-catalyzed loss of the hydroxylic proton. A steady state treatment based on this mechanism yields calculated rates in good agreement with the observed values. Furthermore, the same parameters predict the rates observed at lower pH in the presence of added excess bromide. The Br2 oxidation rate is greater than the HOBr rate by a factor of 60 for benzilic acid, 37 for 2-hydroxy-2-methylpropanoic acid, and 10 for mandelic acid.
The Gas Phase Raman Spectrum and Molecular Structure of Dichlorodibromotellurium(IV) TeCl2Br2. Novel Penta- and Hexa-co-ordinate Mixed Halide Anions of Tellurium(IV). Synthesis and infrared and Raman Spectra of [Et4N]TeCl2Br3 and [Et4N]2TeCl2Br4
Authors: Ozin G. A. , Voet A. Vander
Published: May 2006

The Raman spectrum of gaseous TeCl2Br2 at 310 °C is reported for the first time. The gas phase data is consistent with the presence of a monomolecular species haying C1 symmetry. A synthetic route for the preparation of penta- and hexa-co-ordinate mixed halide anions of tellurium(IV), under anhydrous conditions, is described for the first time. The infrared and Raman spectra for solid [Et4N]TeCl2Br3 and [Et4N]2TeCl2Br4 are reported. A stereochemistry based on a square pyramid, is favored for [Et4N]-TeCl2Br3. In the case of [Et4N]2TeCl2Br4 the vibrational data strongly suggests the presence of a cis-octahedral anion, having C2v symmetry.
The Anomeric Effect: The Conformational Equilibria of Tetrahydro-1,3-oxazines and 1-Methyl-1,3-diazane
Authors: Booth H. , Lemieux R. U.
Published: May 2006

By measurement of CH–NH coupling constants at low temperatures, the N–H axial conformation was shown to be the dominant, or sole, conformation for tetrahydro-1,3-oxazine, tetrahydro-2-methyl-1,3-oxazine, and 1-methyl-1,3-diazane. These results provide further experimental evidence for the generalized anomeric effect. Nuclear Overhauser experiments established the partial axial character of the N-methyl substituent in tetrahydro-3,4,4,6-tetramethyl-1,3-oxazine.The n.m.r. spectral data for a number of tetrahydro-1,3-oxazines and derived salts are tabulated and discussed.
Significance of Heterogeneous Catalysis of Certain Oxidation Reactions by Oxides in Relation to their Heats of Formation
Authors: Vijh Ashok K. , Lenfant P.
Published: May 2006

The significance of previous correlations observed by Morooka et al. between heats of formation per oxygen atom, ΔH0, for oxides and their catalytic activity towards oxidation of some hydrocarbons has been discussed. It has been pointed out that ΔH0 values do not represent metal–oxygen bond energies, as assumed by Morooka and co-workers, but instead signify band gap values for the oxides. The catalytic activity of these oxides must therefore be interpreted in terms of their electronic conductivity and not in relation to the strength of metal–oxygen bond involved.
Chlorination of Heterocyclic and Acyclic Sulfonhydrazones
Authors: King J. F. , Hawson Anne , Huston B. L. , Danks L. J. , Komery J.
Published: May 2006

Chlorination of 2H-1,2,3-benzothiadiazine 1,1-dioxide(1) in wet methylene chloride gives o-formylbenzenesulfonyl chloride (4), but in dry methylene chloride at 0° yields the chlorosultine 3-chloro-3H-2,1-benzoxathiole 1-oxide (2); the latter is readily hydrolyzed to the "pseudo-acid" 3H-2,1-benzoxathiol-3-ol 1-oxide (3) which on further chlorination forms 4. In 1,2-dichloroethane at −20° chlorination of 1 gave the "coupled product" 14, whereas in dimethylformamide at room temperature the cyclic acyl chloride hydrazone 4-chloro-2H-1,2,3-benzothiadiazine was isolated in poor yield. The acyl chloride hydrazones (16) were the products obtained following chlorination of some representative aromatic acyclic tosylhydrazones (15). 3H-2,3,4-Benzothiadiazepine2,2-dioxide (19), a previously unknown heterocyclic system, was synthesized in two steps from 1,3-dihydrobenzo[c]thiophene (17). Chlorinolysis of 19 gave o-chloromethylbenzal chloride (21). These reactions are believed to involve formation of the α-chloroazo compound (e.g. 22) as the first step. The formation of 2 from 1 is discussed in terms of three possible routes, two which involve the sulfene 23.
Dielectric Studies. Part XXXI. Analysis of the Dielectric Data of Phenol and its Polymerized Forms
Authors: Magee M. D. , Walker S.
Published: May 2006

The dielectric absorption and dispersions of several solutions of phenol in p-xylene have been measured at four microwave frequencies and at 2 MHz at a temperature of 25 °C. The data have been analyzed in terms of a mean relaxation time, a distribution parameter, and an apparent dipole moment which are useful empirical parameters for assessing the state of aggregation of the phenol molecules. The relaxation time at the lowest practicable concentration (0.02 mole fraction) is long for a molecule expected to relax predominantly by an intramolecular process. This and the behavior of the relaxation time and apparent dipole moment with increasing concentration are considered in terms of a model based on progressive association into an extended series of multimers, the trimer having a zero (or low) dipole moment and higher multimers becoming increasingly flexible.
A Clathrate Hydrate of Cyclobutanone: Dielectric Relaxation of the Host and Guest Molecules
Authors: Morris B. , Davidson D. W.
Published: May 2006

A low-frequency dielectric study of (CH2)3CO•17H2O shows a water absorption region characteristic of a structure II clathrate hydrate which melts congruently at 0.0 °C. The relatively low Arrhenius energy of 6.5 kcal mol–1 is similar to that of acetone hydrate, for which new results are given. At low temperatures reorientation of encaged cyclobutanone molecules gives a very broad absorption region and a contribution to the static permittivity which falls with decrease of temperature. These properties are attributed to the effects of the electrostatic fields of the orientationally-disordered water molecules, which form the cages. Such fields distort the tetrahedral symmetry of the cages to an extent which varies greatly from cage to cage. The high permittivity (~3.6) at 4.2 °K probably arises from rotational oscillations at frequencies near 20 cm−1 of the guest molecules in shallow potential minima. This enhancement of polarizability removes the difficulty previously noted in the applicability of the Onsager cavity model to structure II hydrates. The dipole moment of cyclobutanone in cyclohexane solution was found to be 2.78 ± 0.02 D.
Coordination Compounds of Olefins with Anhydrous Silver Tetrafluoroborate. VI. Complexes with Vinyl Chloride and Vinyl Fluoride
Authors: Quinn H. W. , Vangilder R. L.
Published: May 2006

The stability of the complexes AgBF4•2 vinyl chloride and AgBF4•2 vinyl fluoride has been determined and compared with that of AgBF4•2 propylene. The much lower stability of the halo-olefin complexes has been attributed partly to weaker interaction of these less basic olefins with the silver ion and partly to configurational restrictions imposed upon the complexed halo-olefin molecules as a result of their higher permanent dipole moment.
Carbon Disulfide. IV. Reaction with Active Methylene Compounds. The Formation of 3,5-Bismethylene-1,2,4-trithiolanes
Authors: Yates Peter , Lynch Thomas R.
Published: May 2006

The three-sulfur compounds formed on oxidation of the β-keto dithio acids prepared by the reaction of active methylene compounds with base and carbon disulfide have been shown to be 3,5-bis(acylmethylene)-1,2,4-trithiolane derivatives. In several cases, two of the three possible geometrical isomers have been isolated and provisional stereochemical assignments have been made. The i.r. and u.v. spectra of the trithiolanes have been compared with those of corresponding 2,4-bis(acylmethylene)-1,3-dithie-tane derivatives (desaurins) and interpreted in terms of a strong conjugative interaction between the sulfur atoms and carbonyl groups.
A Study of Cation-exchange Reactions in the System Potassium Durosemiquinone – Potassium Tetraphenylboride – Tetrahydrofuran
Authors: Gough T. E. , Hindle P. R.
Published: May 2006

The electron spin resonance (e.s.r.) spectrum of potassium durosemiquinone in tetrahydrofuran has been studied as a function of temperature and found to exhibit line-width alternation indicating the presence of an intramolecular migration of the potassium ion between the oxygens of the semiquinone. The addition of potassium tetraphenylboride to the system produces intermolecular scrambling of potassium, the spectral effects of which are superimposed upon those of the intramolecular exchange. From the spectral line-shapes approximate values of the activation energies and frequency factors were derived. The tetraphenylboride anion did not play a detectable role in the various exchange mechanisms.
Carbon Disulfide. V. Reaction with Azibenzil
Authors: Yates Peter , Christensen B. G. , Williams L. L.
Published: May 2006

The product formed by the reaction of azibenzil (2-diazo-2-phenylacetophenone) with carbon disulfide has been shown to be 2-(α-phenylphenacylidene)-5,5-diphenyl-1,3-dithiolan-4-one (9).
Reaction of trans-2-Acylaminocyclanols with Thionyl Chloride
Authors: Bannard R. A. B. , Gibson N. C. C. , Parkkari J. H.
Published: May 2006

trans-2-Acetamidocyclohexanol (1; n = 2, R = CH3) on addition to thionyl chloride in chloroform at 0° was converted rapidly and quantitatively to D,L-2-methyl-4,5-cis-cyclohexanoöxazoline hydrochloride (2; n = 2, R = CH3) judging from shifts in the methyl proton resonances of the n.m.r. spectra of the amide and the reaction solution. The intermediate chlorosulfinate was estimated to have a half-life of less than 2.25 min. The oxazoline salt was isolated in 98% yield by sublimation of the crude product in vacuo and was identified by its i.r. and n.m.r. spectra and by its facile and almost quantitative hydrolysis to cis-2-aminocyclohexanol hydrochloride. The oxazoline salts 2 (n = 1, R = CH3, [Formula: see text] and n = 2, R = C6H5, [Formula: see text]) were readily obtained in 95 % yield or better by the same general method and it was shown that the trans-2-acetamidocyclanols are the preferred starting materials for conversion to cis-2-aminocyclanol derivatives by the thionyl chloride inversion reaction. The oxazoline bases 4 (n = 1, R = CH3, [Formula: see text] and n = 2, R = CH3, [Formula: see text]) were readily obtained in high yield from the corresponding salts and differences in the i.r. and n.m.r. spectral characteristics of the salts and bases are reported.
Metal – Aminopolycarboxylic Acid Complexes. II. Studies of Triethylenetetraaminehexaacetic Acid and its Lead(II) Complexes in Aqueous Solution by Proton Magnetic Resonance Spectroscopy
Authors: Letkeman P. , Westmore J. B.
Published: May 2006

Nuclear magnetic resonance (n.m.r.) spectroscopy was used to determine the preferred protonation sites in TTHA. For its 1:1 complex with Pb(II) the following equilibrium constants for protonation were obtained (triethylenetetraaminehexaacetic acid ≡ H6A)[Formula: see text]The non-protonated complex is considered to have four coplanar (or nearly coplanar) metal–nitrogen bonds with the center carboxylate groups coordinated above and below this plane, and with the terminal carboxylate groups playing only a small part in the coordinate bonding. The first and second protonations of the complex occur preferentially at the terminal and center nitrogen atoms, respectively, on the same side of the complex, accompanied by breaking of the respective metal–nitrogen bonds. This causes partial unwrapping of the complex from one side. Rapid interconversion between configurations in which unwrapping and rewrapping occurs first from one side of the molecule and then from the other leads to simplified n.m.r. spectra.
Mécanisme de la décomposition photosensibilisée au mercure du méthylvinyléther à 2537 Å
Authors: Castonguay J. , Rousseau Y.
Published: May 2006

The study of the mercury Hg6(3P1) photosensitized decomposition of methyl vinyl ether has been studied in a static system at substrate pressures from 10 to 800 Torr. The excited precursor proposed has a calculated lifetime of 1.18 × 10−10 s and its decomposition proceeds almost exclusively through the rupture of the O—CH3 bond. A second primary process is the intramolecular formation of ethylene but it accounts only for 2% of the total ether decomposition. The major products are shown to be formed by free radical reactions and the overall reactivity appears to be very similar to that of the olefins. The results obtained with CH3SH added to the system indicate that the primary radicals are formed with a quantum yield close to unity.
Compressibilities of Porous Glass
Authors: Kipkie W. B. , McIntosh R.
Published: May 2006

Partial extension isotherms have confirmed earlier results that polar adsorbates cause greater extensions than non-polar adsorbates. Data now found for ethyl chloride are in disagreement with those reported by Quinn and McIntosh (3) which are presumed to be in error. Support of this view is provided by consistent values of β′, the compressibility of the glass–adsorbate system, based upon studies with four adsorbates. The consistency now revealed suggests that the mechanism postulated by Quinn and McIntosh is valid for the reversible adsorption along the top of a desorption loop.
Biosynthesis of Lobinaline
Authors: Gupta R. N. , Spenser Ian D.
Published: May 2006

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