摘要:

The method of Clarke and Glew has been used to obtain estimates of the precision of measurement of the thermodynamic functions for the solution of hydrocarbons, the noble gases, and inert diatomic gases in water. In some cases, the precision of the data is such that a statistically significant value for the temperature coefficient of the heat-capacity change for the solution process is obtained. Comparison with the theory of Nemethy and Scheraga shows that their calculations of heat-capacity changes at 25 °C are better than previously believed, but that their prediction of a positive temperature coefficient for this quantity is in contradiction with most data.

ISSN:0008-4042    

DOI:10.1139/v72-022

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Anisotropic hyperfine tensors were calculated for C—H, (C—CH3), allyl, and perinaphthenyl. In the McConnell and Strathdee theory, the anisotropic proton tensor depends primarily on the STO exponent chosen for the 2pπ, carbon atom orbital. By decreasing the exponent ζπfrom the normal Slater value to ~ 1.3, the effect of σ-spin density in the C—H bond could be taken into account. However, this reduction in ζπyields too small a value forwhich governs the anisotropic13C tensor. Contributions to the anisotropic proton and13C hyperfine tensors are discussed, and the results compared with recentabinitiocalculations, as well as single-crystal and liquid crystal data.

ISSN:0008-4042    

DOI:10.1139/v72-023

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

A normal-coordinate analysis of three substituted ethanol molecules X—CH2—CH2—OH (where X = Cl, Br, or CN) was carried out using the simple valence force field model, and a computer program of Schachtschneider translated into Fortran language by Brooks. The effect of internal hydrogen bonding was studied by adding one extra symmetry coordinate, H … X (two, H … C and H … N, in the case of 2-cyanoethanol). The corresponding force constants show a good correlation with the hydrogen bond strengths. Most of the other force constants maintain the same value in thegaucheand thetransrotamers. In general the calculated fundamental frequencies agree closely with the observed ones. The potential energy distribution confirms the extensive coupling between certain vibrations; particularly the skeleton stretching and the CH2twisting and rocking. Only the C—X stretching and the skeleton bending vibrations are strongly affected by rotational isomerism.

ISSN:0008-4042    

DOI:10.1139/v72-024

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Gamma-ray irradiation at 77 °K and X-ray irradiation at room temperature of single crystals of the diamagnetic tetrapotassium hexacyanoruthenate trihydrate have been shown to produce a number of interesting paramagnetic species. At room temperature the e.s.r. spectra can be interpreted in terms of the species [Ru(CN)5(NC)]5−. At liquid nitrogen temperature the species [Ru(CN)4(NC)2]5−is observed and the HCN−radical is produced in an environment which does not permit it to rapidly reorientate at 77 °K. The HCN−radical is believed to be in close association with a ruthenium(II) ion.

ISSN:0008-4042    

DOI:10.1139/v72-025

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The influence of ion-pair intermediates on solvolytic displacement reactions is considered for cases where the observed rate constant is complex.Such complex and composite rate constants under certain conditions may show deviations from the Arrhenius temperature dependence law. The deviations will manifest themselves as "spurious" positive and/or negative heat capacities of activation, superimposed on the real heat capacity terms.The hypothesis of Albery and Robinson (1) which proposes that the heat capacity of activation fort-butyl chloride is entirely "spurious" in the sense outlined above, is critically evaluated and rejected. An alternative hypothesis that considers the heat capacity to be a manifestation of solvation effects is retained.The mechanism of the hydrolysis of both the methyl andt-butyl halides in water is discussed and the kinetic laws appropriate to each are shown to be consistent with real heat capacities of activation. The mechanism proposed differs from the classical SN1–SN2 description. Both series of substrates are considered to give rise to intimate-ion-pairs but in the case of the methyl halides these react further by a path which involves the nucleophilicity of the solvent in a kinetically significant way. In the cases of the tertiary compounds, solvent separation of ion-pairs becomes kinetically significant. The nucleophilic component which characterizes the destruction of the solvent-separated ion-pairs for the tertiary compounds is kinetically insignificant.

ISSN:0008-4042    

DOI:10.1139/v72-026

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The spin–orbit relaxation of Hg(63P1) to yield Hg(63P0) was investigated in the presence of various gases. The quantum yields of Hg(63P0) formation (defined as relaxation to Hg(63P0)/total relaxation) in the presence of CO, CO2, NH3, ND3, H2O, D2O, C2H6,c-C3H6, C(CH3)4, C3H8, 2,2-C3H6D2, C3D8,n-C4H10andi-C4H10were: 0.88 ± 0.07, <0.01, 1.05 ± 0.05, 1.00 ± 0.08, 0.76 ± 0.18, 1.06 ± 0.26, 0.64 ± 0.16, 0.56 ± 0.10, 0.58 ± 0.02, 0.14 ± 0.01, 0.51 ± 0.07, 0.47 ± 0.10, 0.11 ± 0.01, and 0.05 ± 0.01, respectively. The extent of the spin–orbit relaxation process appears to be related in an inverse manner to the availability and accessibility of channels leading to the formation of Hg(61S0), rather than to the fulfillment of electronic–vibrational resonance conditions. This in turn suggests the existence of Hg(63P1)—quencher intermediates having lifetimes long enough to permit several vibrations.

ISSN:0008-4042    

DOI:10.1139/v72-027

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Potentiometric and conductimetric measurements of solutions of sodium hydroxide and lead nitrate at 27 ± 0.2 °C have established the existence of hydrated lead monoxynitrate, dioxynitrate, heptoxytrinitrate and pentoxynitrate. It was shown that the presence of silica inhibits the formation of anhydrous lead oxide but favors that of hydrated lead oxide. The preparation of lead oxynitrates and hydrated lead oxide was carried out over a wide range of temperatures at various concentrations of reactants.

ISSN:0008-4042    

DOI:10.1139/v72-028

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The kinetics and equilibria involved in the formation of monoacetatoiron(III) from iron(III) in aqueous solution has been investigated at ionic strength 0.50 Mand temperatures ranging from 5.2 to 25 °C for kinetic studies and 5.2 to 41 °C for equilibria. The results support the view that the mechanism of the acid independent reaction involves the reactants FeOH2+and CH3COOH in an interchange dissociative (Id) mechanism with ΔH≠ = 11.1 ± 2.2 kcal mol−1. The nature of the acid dependent reactions remains unresolved.

ISSN:0008-4042    

DOI:10.1139/v72-029

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

A number of complexes of FeCl2and FeBr2with amides, ureas, aniline, and benzothiazole have been prepared and characterized by means of Mössbauer and i.r. spectroscopy, and magnetic measurements. The stoichiometries FeX2L, FeX2L2, FeX2L3, FeX2L4, and FeX2L6have been found in which the iron is six coordinate. With the exception of an isobutyramide complex which is formulated as [Fe(BUA)6][FeCl4], complexes of the first three types are polymeric with bridging halogens, while FeX2L4is monomeric and FeX2L6is formulated as [FeL6]Cl2.

ISSN:0008-4042    

DOI:10.1139/v72-030

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

A number of complexes of iron(II) halides with thioamides and ureas have been prepared and characterized by means of Mössbauer, infrared spectroscopy, and magnetic measurements. These complexes are shown to have distorted tetrahedral structures.

ISSN:0008-4042    

DOI:10.1139/v72-031

出版商:NRC Research Press    

年代:1972

数据来源: NRC