摘要:

First order rate constants and activation parameters are reported for the decomposition in chloroform and acetone solvents of a series of 4-substituted-benzylphenyldimethylammonium bromides and iodides and also of a series of tetra-alkylammonium bromides which contain no benzyl group. The results are discussed in terms of general mechanism of these reactions, which are unimolecular "ionic internal" nucleophilic substitutions

ISSN:0008-4042    

DOI:10.1139/v72-203

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Rates of acetolysis of the π acceptor 2,4,7-trinitro-9-fluorenylp-toluenesulfonate, with and without added 9-methylanthracene donor, have been measured at 1, 680, and 1362 atm at 55.2 °C. The volume of activation for acetolysis of uncomplexed ester was −27 cm3mol−1while that for acetolysis of the 1:1 complex was −33 cm3mol−1, relative to uncomplexed reactants. The mechanistic significance of these results is discussed.

ISSN:0008-4042    

DOI:10.1139/v72-204

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Several pyridine carboxylate complexes of cobalt(II) and nickel(II) have been prepared and their spectral and magnetic properties and X-ray powder patterns used to establish their stereochemistry. The cobalt(II) complex of pyridine-3-carboxylic acid Co[3-py(CO2)]2•4H2O, whose crystal structure we have previously reported, was used as a model for a consideration of the structural details of these complexes. Like the latter cobalt(II) derivative, the nickel(II) complex of pyridine-3-carboxylic acid and the cobalt(II) and nickel(II) complexes of pyridine-4-carboxylic acid and pyridine-3-sulfonic acid, isolated as their tetrahydrates, are formulated as non-classical zwitterions. Comparisons are made with the related pyridine carboxylate complexes of silver(II).

ISSN:0008-4042    

DOI:10.1139/v72-205

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The crystal structure of tetrameric phosphonitrilic isothiocyanate, N4P4(NCS)8, has been determined by three-dimensional X-ray studies from data collected on a Picker FACS-1 automated diffractometer. The compound crystallizes in the triclinic space groupwitha = 8.098(8),b = 8.018(7), c = 9.937(10) Å, α = 104.08(7), β = 99.42(7), γ = 95.42(7)°, and one molecule per unit cell. The structure was solved from 1766 independent non-zero reflections and refined to a conventionalRfactor of 0.063. Nitrogen atoms of two isothiocyanate groups are bonded to each phosphorus atom of the eight-membered phosphorus–nitrogen ring. The ring has a chair configuration. The average dimensions of the structure are P—Nring = 1.543 + 0.017, P—Nisothiocyanate = 1.644 ± 0.011, N—C = 1.168 ± 0.008, C—S = 1.535 + 0.009 Å,and NĈS = 176.6 ± 1.1°

ISSN:0008-4042    

DOI:10.1139/v72-206

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Differential scanning calorimetric curves have been obtained corresponding to the desorption of hydrogen from palladium and palladium–silver alloys. There was no evidence for the existence of an exotherm, following the endothermic desorption of hydrogen, which has been previously found and attributed to the relaxation of a metastable, expanded hydrogen-free palladium lattice. Heats of desorption have been evaluated from the areas of the endotherms and these are reasonable in the light of values obtained by other techniques. Comparisons of scanning curves for palladized and unpalladized hydrogen-containing silver–palladium alloys demonstrate that solid-state diffusion cannot be the slow step for the former but may be for the latter.

ISSN:0008-4042    

DOI:10.1139/v72-207

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Complexes of the type Pt(ac)2where ac = R1R2C(OH)—C≡C—C(OH)R1R2have been studied. The compounds are mononuclear, non ionic, and diamagnetic. The experimental results seem to indicate that the ligands are not rearranged in the complex. The order of the triple bond has been partially reduced and there is an important distortion of the acetylenic molecule. A structure with the two ligands hydrogen bonded is proposed.The complexes Pt(ac)2react with triphenylphosphine according to the following equation:

ISSN:0008-4042    

DOI:10.1139/v72-208

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The fluorescence and phosphorescence yields on photolysis of 2,3-pentanedione were investigated at various temperatures. The processes involved in the formation and removal of both the singlet and triplet states are considered. The data agree qualitatively and quantitatively with the results of an earlier study of the lifetime of the triplet state. It is shown that delayed fluorescence is not observed in the pentanedione system. A mechanism is proposed that can correlate the temperature variation of both the lifetime and quantum yield data.

ISSN:0008-4042    

DOI:10.1139/v72-209

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Vibrationally excited singlet and triplet states of 2,3-pentanedione are formed by photolysis at 365 nm. The processes removing these excited states in the gas phase are studied by measuring the fluorescence and phosphorescence yields. Fluorescence can occur from the vibrationally excited, as well as the vibrationally equilibrated, singlet state. The fluorescence and phosphorescence data are considered in terms of mechanisms which involve either weak or strong collisions. Although the data cannot distinguish between the alternatives, there are two significant conclusions. The fluorescence data require that emission occur from at least two levels in the singlet manifold. To explain the phosphorescence data, the highest emitting singlet level must not lead to a vibrationally equilibrated triplet state.

ISSN:0008-4042    

DOI:10.1139/v72-210

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The enthalpies of mixing for a reacting charge asymmetrical ternary molten salt system have been calculated on the basis of an extension of a previously developed model for binary systems. The enthalpy of mixing is considered to consist of a reaction term and a mixing term; the former results from the formation of the tetrahedrally coordinated complex speciesand the latter from the mixing of the products of reaction according to quasichemical theory modified to account for charge asymmetry.The ternary model enables the prediction of the integral enthalpies from a knowledge of the interaction parameters determined for the two charge asymmetrical binary systems. The calculations are compared with experimentally measured integral enthalpies of mixing in the ternary system MnCl2–NaCl–CsCl, and shown to give accurate predictions of the behaviour of the system.

ISSN:0008-4042    

DOI:10.1139/v72-211

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The temperature dependence of the rate of solvolysis oft-butyl chloride in mixtures of tetrahydrofuran and of acetonitrile in water have been determined. In the high-water range both minor co-solvents lead to a reduction in the value of ΔH≠similar to that found previously where alcohol was the co-solvent. However, a remarkable difference in the values ofacross the same concentration range reflected a difference in the effect of these two co-solvents on the structural properties of the several solvent media. Where tetrahydrofuran or alcohols are the minor co-solvent,becomes much more negative until that concentration is reached where the quasi-aqueous structure collapses. Where acetonitrile is the minor co-solventbecomes more positive relative to the value found for hydrolysis in water until a value of about −40 cal deg−1mol−1is reached. The implication of these findings concerning the nature of solvation of weakly polar solutes in such mixtures is discussed.

ISSN:0008-4042    

DOI:10.1139/v72-212

出版商:NRC Research Press    

年代:1972

数据来源: NRC