摘要:

The complete ladder of ΔG10determinations obtained from measurements of some 110 gas phase proton transfer equilibria A1− + A2H = A1H + A2−involving some 60 acids AH and connecting to the standard acid HCl is given. Evaluation of the entropy changes leads to values for the deprotonation energies ΔHD0and ΔGD0(at room temperature) corresponding to the gas phase process AH = A− + H+; ΔHD0 = D(A—H) − EA(A) + 313.6 kcal/mol. Comparison of the present data with literature determinations of the bond dissociation energies and electron affinities shows agreement within 2 kcal/mol. Some experimentally determined entropy changes ΔS10are compared with the theoretically calculated values.

ISSN:0008-4042    

DOI:10.1139/v78-001

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The catalytic reaction between carbon monoxide and nitrous oxide has been studied on MnO from 493 to 573 K and on Co3O4from 383 to 493 K. The apparent activation energy on MnO was 130 ± 4 kJ mol−1, while for Co3O4, a change from 31 ± 4 to 105 ± 4 kJ mol−1was observed at 450 K. The rate-controlling step for the catalytic reaction on MnO was associated with the surface reaction between carbon monoxide and nitrous oxide in a manner similar to that previously reported for NiO, while for Co3O4, the rate-determining step was related to the formation of an intermediate surface carbonate. The changes inEAmay be a consequence of the surface reaction proceeding via a concerted redox reaction in the low temperature region and then to a stepwise mechanism at higher temperatures resulting from the presence of structurally and energetically different forms of the intermediate surface carbonate.

ISSN:0008-4042    

DOI:10.1139/v78-002

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Suggestions that e−(aq)is involved as a reactant in reduction reactions at metal electrodes are examined. It is shown that an experimental test of the participation of e−(aq)can be devised. The results of this test show that the conventional theory, involving electron transfer directly from the electrode to the species being reduced, provides a better explanation of the reduction process in aqueous solution.

ISSN:0008-4042    

DOI:10.1139/v78-003

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Measurements at 25 °C with flow calorimeters and densimeters have led to heat capacities and densities of aqueous solutions of 11 1:1 electrolytes: NaClO3, NaBrO3, NaIO3, NaNO3, NaClO4, NH4NO3, KClO3, KBrO3, KIO3, NH4Cl, and NH4ClO4. The first 6 salts were studied up to near saturation. We have used results of these measurements to obtain apparent molal heat capacities and apparent molal volumes of the various solutes. Extrapolation to infinite dilution on the basis of the Debye–Hückel theory bas led toandvalues for each solute. We have compared these standard values with results of earlier investigations.

ISSN:0008-4042    

DOI:10.1139/v78-004

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Monofluorocyclopropane isomerizes at 475 °C to formcis- andtrans-1-fluoropropene, 2-fluoropropene, and 3-fluoropropene. The relative amounts of these products formed are pressure dependent. It is shown that, using the previously determined Arrhenius parameters for the formation of each product, RRKM theory does account satisfactorily for the pressure dependence of the product yields forallthe reaction products.

ISSN:0008-4042    

DOI:10.1139/v78-005

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The transformation of aragonite to calcite (A–C) is an irreversible reconstructive transformation involving a change from 6 to 9 in the primary coordination. Cationic impurities like Na+, Mg2+, Zn2+, Y3+, La3+, Nd3+, Gd3+, Dy3+have been doped in pure aragonite and their effect on the kinetics and energetics of its transformation to calcite is studied. By employing a DTA technique, the enthalpy and energy of activation for the transformation have been calculated. The ir spectra of aragonite and calcite in pure form and with various impurities have been studied and the effect of impurities on absorption bands discussed.

ISSN:0008-4042    

DOI:10.1139/v78-006

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

On the basis of the long-range couplings over six bonds between the protons on the side chain and the ring protons in benzal fluoride, chloride, and bromide and some of their derivatives, a hindered rotor model (Jmethod) yields limits to the barriers to internal rotation. These are 0.0 to 1.8, 0.7 to 2.4, and 1.7 to 3.8 kcal/mol for the fluoride, chloride, and bromide, respectively. Refinement of the model suggests barriers of 1.1 ± 0.2, 2.2 ± 0.3, and 3.5 ± 0.6 kcal/mol, respectively. The barrier values in the chloride and bromide are considerably less sensitive to the model parameters than is the barrier in the fluoride. It would be of interest to have gas phase values for these barriers. It is also shown that a σ–π mechanism holds for the six-bond proton–proton coupling constant in benzal fluoride but that the analogous coupling between19F on the side chain and thepararing proton carries a non σ–π contribution of +0.3 Hz.

ISSN:0008-4042    

DOI:10.1139/v78-007

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

A study of several different reductions of α, β-unsaturated nitriles by NaBH4shows that these proceed by way of a 1:4 addition to form saturated nitriles. At long reaction times, hydrolysis products or those of substitution of the saturated nitrile are observed. The relative rates of reduction follow the order: 2-phenyl-2-butenenitrile1 > 2,3-diphenyl-2-propenenitrile2 > 3-phenyl-2-propenenitrile3 > 2-butenenitriIe4. [Journal translation]

ISSN:0008-4042    

DOI:10.1139/v78-008

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Carbon-13 nmr spectra of 18 thiazoles with different substituents (R = CH3, C6H5, Cl, Br, NH2et N3) have been recorded. The13C chemical shifts and thenJ(C,H) coupling constants are discussed as a function of the nature of the substituent and the electronic structure of the thiazole ring. The 2-azido substituted thiazoles show azido-tetrazole isomerism, making possible a comparative study of substituent effects in thiazole and thiazolotetrazole rings. These studies have been extended to other heterocycles: benzothiazole, isothiazole, and isoxazole.

ISSN:0008-4042    

DOI:10.1139/v78-009

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The configuration of the sulfoxide oxygen insyn- andanti-thiobinupharidine sulfoxide was determined by employing the13C nmr sulfoxidation increments of C-6. Establishment of the13C nmr line assignments for C-6 included the study of the C-6 and C-6′ deuterated thiobinupharidine and the corresponding sulfoxides. Thermolysis ofsyn-thiobinupharidine sulfoxide in DMSO and subsequent reduction with sodium borodeuteride in methanol yielded thiobinupharidine, labelled with deuterium only at C-6, and thionuphlutine B, labelled with deuterium at both C-6 and C-6′. Treatment of theantisulfoxide in xylene or DMSO resulted in no thiobinupharidine or thionuphlutine B. Similarly,syn-neothiobinupharidine sulfoxide gave neothiobinupharidine and a new thiaspirane, thionuphlutine C. These two compounds were not produced fromanti-neothiobinupharidine sulfoxide heated in xylene.

ISSN:0008-4042    

DOI:10.1139/v78-010

出版商:NRC Research Press    

年代:1978

数据来源: NRC