摘要:

The13C chemical shift,T1and2HT1data for 2-butoxyethanol (BE) in D2O as a function of concentration are presented. The nmr parameters are consistent with thermodynamic data for the same system in that it appears that 2-butoxyethanol in water undergoes a pseudo phase transition at about 1.2 M. The chemical shift for each carbon is different in the microphase relative to either aqueous solution or pure BE. The shift differences are due to a combination of factors, conformer population changes, changes in the polarity of the oxygen, and a solvent effect on chemical shift. The more organic the medium, the higher the population oftransrelative togaucheconformers. The motion of BE is more restricted in the microphase than in either dilute aqueous solution or in the pure liquid. The number of adsorbed D2O molecules per molecule of BE is less in the microphase than in aqueous solution.

ISSN:0008-4042    

DOI:10.1139/v84-011

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Optical absorption and photoconductivity spectra of trapped electrons in -γ-irradiated 2,2,4-trimethylpentane (TMP)/2,2-dimethylbutane (DMB)/2-methyltetrahydrofuran (MTHF) mixture glasses at 77 K have been measured. It is found that the magnitude of the photocurrent increases with decreasing MTHF concentration, which is ascribed to the increase in electron mobility with decreasing MTHF concentration in TMP/DMB/MTHF systems. It is also found that the photoconductivity spectra shift to the lower energy side with decreasing MTHF concentration. Although the photoconductivity spectrum in the neat MTHF system is separated from the corresponding optical absorption spectrum, the spectrum becomes closer to the latter with decreasing MTHF concentration in TMP/DMB/MTHF systems. This result indicates that the extent of bound–free transitions increases relative to bound–bound transitions with decreasing MTHF concentration for the photon absorption process of trapped electrons in TMP/DMB/MTHF systems.

ISSN:0008-4042    

DOI:10.1139/v84-012

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Reaction of sulfolane (tetrahydrothiophene 1,1-dioxide) (1) with methyl fluoride – antimony pentafluoride in liquid sulfur dioxide gives crystalline tetrahydro-1-methoxythiophenium 1-oxide hexafluoroantimonate (2), thereby providing the first characterized example of an alkoxysulfoxonium salt. This salt (2) is also formed, but more slowly, by reaction of methyl fluoride with the crystalline 1:1 complex of sulfolane and antimony pentafluoride. Reaction of2with nucleophiles leads to transfer of the methyl group, a facile process even with such weak nucleophiles as nitrobenzene and phenylN,N-dimethylsulfamate. Spectroscopic evidence has been obtained forO-methylation of other sulfones, either by reaction with MeF•SbF5•SO2, or via the sulfone•SbF5complex and methyl fluoride, or by transmethylation with2.

ISSN:0008-4042    

DOI:10.1139/v84-013

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The acid-catalyzed hydrolysis of the nine-membered ring cyclic vinyl ether, oxacyclonon-2,8-diene, occurs with a normal isotope effect,, which indicates that this reaction proceeds by the conventional vinyl ether hydrolysis mechanism involving rate-determining proton transfer to carbon. The specific rate of this reaction,, may then be used to show that there is no significant ring-size effect on the rate of hydrolysis of a vinyl ether group in a nine-membered ring. The previously noted unusually great reactivity of the vinyl ether group in 9-methoxyoxacyclonon-2-ene, for which an unorthodox reaction mechanism has been claimed, must therefore be due to some other cause.

ISSN:0008-4042    

DOI:10.1139/v84-014

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The effects of buffer, pH, reaction time, and [enzyme]/[substrate] ratio on the enantiomeric purities of the alcohol products of horse liver alcohol dehydrogenase-catalyzed reductions of (±)-α-alkylcyclohexanones and -tetrahydrothiopyranones have been studied. For poor substrates of this type, formation of enantiomerically pure products is assured when pH 8 and < 0.5 × 10−4[E]/[S] ratio conditions are used.

ISSN:0008-4042    

DOI:10.1139/v84-015

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The salting-out of triethylphosphate (TEP) from water was measured at 25 °C for twelve inorganic electrolytes. If salting out is taken as an additive property of ions, then the effectiveness for salting TEP out of water isfor anions andfor cations. The results were fitted to three theories. The distribution theory of Conway, Desnoyers, and Smith predicts the order of magnitude of the experimental results, but does not discriminate well between salts of the same valence type. The electrostriction theory of McDevit and Long discriminates well between ions but gives results three or five times larger than those observed. Scaled particle theory predicts the results reasonably well, but the predictions depend critically on the choice of ionic and molecular parameters. Thus, none of these theories is entirely satisfactory.

ISSN:0008-4042    

DOI:10.1139/v84-016

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

A system for the measurement of rate constants for elementary reactions of hydrogen atoms in the temperature region of 1000 K is described. The concentration of hydrogen atoms is controlled by the equilibrium constant for dissociation of hydrogen molecules. The kinetics of the rate of conversion of ethane to ethylene in this system has been studied over the temperature range 876–1016 K. The results show that the rate-controlling step isand the value obtained for the rate constant is(R = 1.987 cal mol−1 deg−1). This value is compared with values obtained from other methods over the temperature range 300–1400 K. Combination with a recent measurement of the rate constant for the reverse reaction yields an experimental value for the equilibrium constant for the reaction.

ISSN:0008-4042    

DOI:10.1139/v84-017

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Carbon-13 and nitrogen-15 nmr chemical shifts of benzenediazonium salt and itspara-substituted derivatives have been measured in sulfolane solutions. The chemcial shifts of13C1 correlate linearly with the polarographic half-wave potentials. This relation indicates the linear increase of electron densities at C1 with the increase of electron-donating power of the substituents. Non-linear relationships between15N shifts of both nitrogen nuclei and the half-wave potentials were partly attributed to the second-order paramagnetic contributions to the15N shifts. This contribution is approximately proportional to the inverse of the uv absorption frequencies. Overall results suggest that in the ground state resonance structures of the benzenediazonium salts, the rehybridization of the C1—N1 bond is very unlikely and this bond remains as a single bond.

ISSN:0008-4042    

DOI:10.1139/v84-018

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Preparative-scale high pressure liquid chromatography on 3-acetyl-2-(2′,6′-dimethyl-5′-heptenyl)oxazolidine (1), a complex acetamide derivative of citronellal, resulted in isolation of the diastereomeric forms of this insect repellent. The two diastereomers were designated as1aand1bon the basis of their order of elution from silica gel and from a variety of capillary gas chromatography columns. Interpretation of the13C nuclear magnetic resonance spectra of1aand1bwas accomplished by comparison with model compounds and by off-resonance proton-decoupling experiments. Absolute stereochemical assignments were not made. Because of the amide group, the diastereomers existed in solution at ambient temperature ascisandtransrotational isomers, which caused nonequivalence of most of the carbon atoms, including the olefinic carbons at C-5′ and C-6′.transIsomer (5) was concluded to be the major contributor to the rotational equilibrium. The spectrum of 3-acetyl-2-(4′-methyl-3′-pentenyl)oxazolidine (7) was also recorded for comparison.

ISSN:0008-4042    

DOI:10.1139/v84-019

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Proton nmr studies of cubane mono and 1,4-dicarboxylic acids in lyotropic liquid crystalline solution show that these molecules are distorted from the cubane structure. The protons of cubane dicarboxylate which are vicinal to their respective carboxylate group are displaced towards those groups along theC3axis resulting in an elongation relative to a cube. In cubane monocarboxylate there is also a displacement of vicinal protons toward the carboxyl group, but this is accompanied by a displacement of the protons one carbon further removed, away from the carboxyl groups. The shape of this latter compound is comparable to that of a section of a cone with the narrow end of the cone defining the proton positions adjacent to the carboxyl group while the wide end of the cone defines the positions of the adjacent set of protons. The remaining proton of course sits on theC3axis which determines the centre of symmetry of the cone.

ISSN:0008-4042    

DOI:10.1139/v84-020

出版商:NRC Research Press    

年代:1984

数据来源: NRC