摘要:

Volume changes at a mercury cathode in hydrogen-saturated aqueous 0.1 Mhydrochloric acid during electrolysis at 25 °C are less than those predicted by Faraday's Lawover 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.

ISSN:0008-4042    

DOI:10.1139/v70-034

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The molar excess enthalpies and volumes of the systems cyclohexane –cis-decalin and cyclohexane –trans-decalin at 25 °C were determined by direct calorimetric and dilatometric measurements. The Flory theory of mixtures provides a useful basis for a qualitative interpretation of the results.

ISSN:0008-4042    

DOI:10.1139/v70-035

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

One of the compounds obtained by the reaction of rhenium(III) chloride withn-butyric acid while exposed to oxygen has been shown by single crystal X-ray diffraction to be tetra-μ-n-butyratodi-rhenium(III) diperrhenate. The crystals are triclinic with lattice parametersa = 7.836(8) Å,b = 10.746(8) Å,c = 8.773(8) Å, α = 88.9(1)°, β = 106.5(1)°, and γ = 98.0(1)°. The space group isand there is one formula unit per cell. A total of 1593 independent reflections were examined and the structure was refined by full 3-dimensional least-squares to anRvalue of 0.123. Two rhenium environments are found, one consisting of a dimer unit bridged by 4 carboxylate groups and the other a per-rhenate group. This latter group, showing a mean Re—O distance of 1.75 Å, shares an oxygen atom with a rhenium atom in the dimer unit, and this Re—O bond length is 2.18 Å long. The structure results from packing of short chains, consisting of the dimer unit and the 2 perrhenate groups, running roughly parallel to the [111] direction.

ISSN:0008-4042    

DOI:10.1139/v70-036

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Values of 1.7 × 108 s−1and 2.5 × 107 M−1s−1forkd, the unimolecular rate constant for decay, andkr, the rate constant for addition to cyclohexene, have been obtained for cyclohexenone. These indicate that this cyclenone decays somewhat faster and reacts significantly slower with the same substrate (in the same solvent) than does cyclopentenone. Evidence is adduced, from sensitization experiments and the phosphorescence quenching of a range of carbonyl compounds, that the reactive triplet and lowest triplet of cyclohexenone lie close together, if they are indeed not identical, and the energy of this triplet is in the region of 66–68 kcal/mole. This is higher than that indicated by photostationary state measurements. This latter method, applied to cyclenones, may be suspect, and triplet energies so derived subject to doubt (that of cyclopentenone included) or have a different significance from those obtained by other methods. Further attempts to demonstrate the existence of a lower, cycloadditively unreactive, triplet in cyclopentenone have been negative. It now seems far more likely that the original interpretation was in error, that the lowest energy triplet is near 73 kcal/mole, and that a special mechanism for quenching benzophenone triplets by ground state cyclopentenone exists. The evidence for other multiple reactive triplets is re-examined as is the evidence for the nature of the states involved.

ISSN:0008-4042    

DOI:10.1139/v70-037

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The irradiation of 2-pyrone in benzene followed by pyrolysis gives a poor yield of cyclooctatetraene. The irradiation of 4-methoxy-6-methyl-2-pyrone in water givescis-β-methyl glutaconic half ester and the corresponding diacid. Irradiation in benzene followed by the addition of water gives a mixture of thecisandtransglutaconic derivatives. It is believed that these substances derive from the β-lactone formed by irradiation, and support for this view is obtained from low temperature irradiations. An oligomeric intermediate (16) is suggested as a second intermediate in the irradiation in benzene, and a hemiketal (20) in the aqueous irradiation.

ISSN:0008-4042    

DOI:10.1139/v70-038

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The relaxation behavior of some amides was investigated in their high resolution spectra by the direct saturation–recovery and Overhauser effect methods. The recovery curves and steady-state Overhauser effects were obtained for solutions of dimethylformamide with double- and triple-resonance irradiations. The results were analyzed for 3- and 4-spin systems and the values of relaxation parameters were calculated. It was shown that for dimethylformamide the one-exponential recovery curve approximation gives theT1values with a precision better than experimental error (±2%). The observed difference in relaxation times for methyl group protons was explained by different correlation times and more restricted rotation of 1 of the groups. The correlation times for dipole–dipole interactions of methyl groups with the formyl proton were also evaluated with some reasonable assumptions.The change of the relaxation rate ofN-methyl protons in C6H6and C6D6solutions was explained by formation of the collision complex with amide molecules and specific intermolecular dipole–dipole proton interaction. This effect could be useful for determination of thecis- andtrans-conformations inN-methyl substituted amides and peptides as an absolute method because it does not require measurements on both isomers.

ISSN:0008-4042    

DOI:10.1139/v70-039

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

A general method for the synthesis of 6-amino-6-deoxy-α-D-glucopyranosides from 3,4-di-O-acetyl-1,2-dideoxy-6-O-p-tolylsulfonyl-D-arabino-hex-1-enopyranose (3,4-di-O-acetyl-6-O-p-tolylsulfonyl-D-glucal) is described. The key steps in the synthesis are addition of nitrosyl chloride to the above glycal, condensation of the resulting nitroso–chloro adduct with alcohols or phenols to provide α-glycosides of 3,4-di-O-acetyl-2-oximino-6-O-p-tolylsulfonyl-D-arabino-hexopyranose, and conversion of the α-oximino-glycosides to α-glucoside derivatives. Propyl, isopropyl, phenyl, andL-menthyl 2,3,4-tri-O-acetyl-6-O-p-tolylsulfonyl-α-D-glucopyranosides are thus prepared and the last compound is converted toL-menthyl 6-amino-6-deoxy-α-D-glucopyranoside.

ISSN:0008-4042    

DOI:10.1139/v70-040

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Proton magnetic resonance spectroscopy has been used to examine the deuterium exchange of the methyl protons in two lumazine derivatives. The exchange occurs at the C-7 methyl group in 6,7,8-trimethyllumazine (2) and at the C-6 methyl group in 1,7-dihydro-6,7,8-trimethyllumazine (3). The former reaction is subject to both general acid- and general base-catalysis but the latter only to general acid-catalysis. Plausible mechanisms for the reactions of both compounds are advanced, involving in the case of3, acid-catalyzed addition of water across the C6—N5double bond.

ISSN:0008-4042    

DOI:10.1139/v70-041

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

Saturated aqueous chloroform solutions (0.07 M) with pHranging from 0.8 to 12.6 have been irradiated with60Co γ-radiation in the presence and absence of air.G(Cl− + ClO−) increases with increasing pHin the pHrange 1–3 (aerated solutions) or 3–6 (deaerated solutions) and again at pHgreater than 10.5. The variation in yield from aerated solutions in the region pH1–3 is attributed to competition between chloroform and hydrogen ions for hydrated electrons. However, such competition cannot account for the pHeffect observed in deaerated solutions between pH3 and 6. Increased yields from both aerated and deaerated solutions at high pHare attributed to the formation of O−by reaction of hydroxyl radicals and hydroxide ions. Formic acid and oxalic acid have been identified as minor products when aerated chloroform solutions are irradiated.

ISSN:0008-4042    

DOI:10.1139/v70-042

出版商:NRC Research Press    

年代:1970

数据来源: NRC

摘要:

The saturation pressures and vapor–liquid compositions of 7 mixtures of the system acetone–benzene have been determined from a temperature of 100 °C and a pressure of about 2 atm up to the highest temperatures and pressures at which liquid and vapor coexist. The critical temperatures were determined by the disappearance-of-meniscus method.TheP–T–Xrelations at the liquid–vapor phase boundaries, as obtained by the determination of the bubble-point pressure vs. temperature curves of a series of mixtures of known composition, do not indicate the existence of an azeotrope in the range of temperature and pressure of this research. The binary data have been treated thermodynamically to yield the liquid-phase activity coefficients. The partial molal volumes in the liquid mixture required for the Poynting correction (effect of pressure on liquid phase properties) for liquid-phase activity coefficients have also been obtained. The fugacity coefficient of a component in the vapor mixture has been obtained by a modified Redlich–Kwong equation, as suggested by Chueh and Prausnitz. Following their modification of the van Laar equation, several binary liquid phase parameters, such as the binary interaction constant, Henry's constant and dilation constant, as required for the solution model for excess Gibbs energy, have been calculated.

ISSN:0008-4042    

DOI:10.1139/v70-043

出版商:NRC Research Press    

年代:1970

数据来源: NRC