摘要:

The11B—19F spin–spin coupling constant in AgBF4is shown to have an opposite sign in water from that found in a number of organic solvents. Application of the hypothesis of Bell and Danyluk indicates that it has a positive sign in water. Evidence is presented for association, probably in the form of solvent-separated ion pairs, in aqueous LiBF4and NaBF4solutions, and for the formation of more tightly bound ion pairs in solvents of lower dielectric constant. In contrast, there apparently is no solute association in AgBF4solutions in water, DMSO, DMF, or acetonitrile. The pronounced changes observed in the11B—19F coupling constant support the postulate that its small size is a result of near cancellation of large opposing terms.The collapse of the10B—11B isotope shift at high temperatures in the19F spectra of solutions of AgBF4in acetonitrile and in acetone provides evidence for exchange of fluorine among boron atoms; a mechanism is proposed for this process.

ISSN:0008-4042    

DOI:10.1139/v68-268

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

The reversible potentials for the formation cellhave been measured for concentrations of silver sulfide in silver chloride up to 12 mole %, in the temperature range 490 to 860 °C. Nernst behavior with respect to the partial pressures of the various sulfur species present in the vapor phase over the electrode is observed in the range 10−3to 1.0 atm. Calculations of partial pressures are based on existing mass spectrometric data. The concentration dependence of the cell voltage follows the Nernst law only in very dilute silver sulfide solutions. The data are used to calculate the thermodynamic properties of silver sulfide in solution with silver chloride.

ISSN:0008-4042    

DOI:10.1139/v68-269

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

The exchange kinetics of zinc vapor with polycrystalline zinc selenide have been studied in a static system in the temperature range 720–800 °C.The kinetic data are consistent with a diffusion-controlled process from the initial stage, in contrast with existing exchange data on ZnO and ZnS powders. The diffusion equation is given as:

ISSN:0008-4042    

DOI:10.1139/v68-270

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

The radical yields of C2H5•and CCl3•observed by electron spin resonance of CCl4 + C2H5I mixtures irradiated by γ rays at 77°K are compared with yields of HCl, I2, and HI measured after thawing. The dissociative capture of thermalized electrons by CCl4is extremely effective and accounts for most of the observed radicals. The difference between yields of HCl and CCl3•results from charge transfer from C2H5I+to CCl3•. The formation of iodine proceeds both from neutralization processes of Cl−ions with positive ions formed from C2H5I, and from ion–molecule reactions.

ISSN:0008-4042    

DOI:10.1139/v68-271

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

The enthalpy of reaction of In(CH3)3,c with a chloroform solution of bromine is −162.5 kcal mole−1. With this value ΔHf0298[In(CH3)3,c] = 29.5 kcal mole−1and ΔHf0298[In(CH3)3,g] = 41.1 kcal mole−1. Combining the latter with ΔHf0298[CH3,g] = 33.2 kcal mole−1and ΔHf0298[In,g] = 58.2 kcal mole−1then givesE(In—CH3) = 38.9 kcal mole−1. From previous kinetic studiesD[(CH3)2In—CH3] + D[In—CH3] = 87.9 kcal mole−1. HenceD[CH3In—CH3] = 28.8 kcal mole−1.

ISSN:0008-4042    

DOI:10.1139/v68-272

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

A thermodynamic analysis of the interface between a metal and an ionic crystal is performed and a differential equation for the potential difference Φ between the electrode and the crystal is derived. This equation can be used to give a new expression for the heterogeneous contribution to the thermoelectric power of an ionic crystal MX between electrodes M′. Addition of the homogeneous contribution gives the total thermoelectric power θ. A completeapriorievaluation of this expression for θ is only possible by making assumptions about the contribution to the potential difference between the surface and bulk of the crystal, φS– φB, which comes from the relaxation of cations and anions in the surface layers of an ionic crystal. Some information on this point is provided by the marked decrease in θ which occurs at low temperatures. While an analysis of experimental data in terms of the theory provides acceptable values for the ionic heats of transport, there is, as yet, no explanation of the remarkable Λ-point in the thermoelectric power of pure KC

ISSN:0008-4042    

DOI:10.1139/v68-273

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

The Ostwald's partition coefficient for the solubility of methyl iodide in water was determined from 4.85 to 68.5 °C. The partition coefficient measured for 10−7to 10−8 Msolutions was found to be from 20 to 30% lower than for 10−2 Msolutions. A new rapid gas chromatographic technique is described for the determination of partition coefficients in dilute systems.

ISSN:0008-4042    

DOI:10.1139/v68-274

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

The dipole moments of methyl-, ethyl-,n-propyl-,n-butyl-,n-amyl-, and phenyl-fluoroformate were determined in dilute benzene solutions at 25 °C. The experimental results suggest that the conformation of the fiuoro-esters is similar to the conformation of the chloro-esters and differs from the conformation of the normal esters; viz. the ester hydrocarbon group and the fluorine atom arecisto each other. Results of fluorine and proton n.m.r. measurements on these molecules support the conclusions based on the dipole moment data if a "through-space" coupling mechanism is assumed for the long range spin–spin couplingJH–F1−5.

ISSN:0008-4042    

DOI:10.1139/v68-275

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

A number of phosphine tetracarbonyl halide salts of the Group VI metals have been prepared of the type:cis-[Et4N][PR3M(CO)4X] where PR3 = (p-FC6H4)3P or (p-ClC6H4)3P, M = Cr or Mo for X = Cl, and M = Mo for X = Br, by the reaction of phosphines with the pentacarbonyl halides [Et4N][M(CO)5X]. A new method for the preparation ofcis-complexes from the phosphine tetracarbonyl halides is described.Assignments are made for the bands in the carbonyl stretching region of the infrared spectra of these complexes.

ISSN:0008-4042    

DOI:10.1139/v68-276

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

The kinetics in diglyme are reported for the two reactions of [Et4N][M(CO)5X] with aryl phosphines to formcis-[Et4N][PR3M(CO)4X] and PR3M(CO)5where M = Cr, Mo, or W, X = Cl, Br, or I, and(p-FC6H4)3P, or (p-ClC6H4)3P. The reactions ofcis-[Et4N][PR3M(CO)4X] with excess phos-phine to form (PR3)2M(CO)4have also been studied kinetically. Possible mechanisms for these three types of reactions are discussed.

ISSN:0008-4042    

DOI:10.1139/v68-277

出版商:NRC Research Press    

年代:1968

数据来源: NRC