F.t.i.r. and Raman spectra of triphenylphosphine,triphenylarsine, triphenylstibine,and dibenzylsulphide

The f.t.i.r. and Raman spectra of triphenylphosphine, triphenylarsine, triphenylstibine, and dibenzylsulphide in the solid state at ca 80 K have been recorded over the ranges 3500-40 cm⁻¹ (infra-red, 1 cm⁻¹ resolution) and 1650-30 cm⁻¹ (Raman, 2 cm⁻¹ resolution). The data, particularly those in the low wavenumber region, are more extensive, more complete, and of higher quality than those obtained in previous studies. Detailed band assignments are given.     

Chemistry of Interfaces,M. J. Jaycock and G. D. Parfitt. Halstead Press,John Wiley and Sons,New York, 1981. 279 pp. $90. Paul Becher,Wilmington

A unique physical model is proposed for relating the dimensions and properties of droplets in aqueous diesel fuel invert mlcroemulsions to the measured water vapor pressures over such systems. The model assumes discrete droplets containing surfactant-sheathed liquid cores. A dynamic equilibrium condition is visualized wherein a closed mass transfer cycle e3tists, involving the movement of water molecules from the droplet interior, through the surfactant sheath into the continuous medium and vapor space above the pool. The flat-surface fugacity of the liquid water in the aqueous core would be reduced relative to that of normal water because of Increased intermolecular association stemming from high pressure in the aqueous core caused by surface tension forces. The possible presence of dissolved surfactant constituents would reduce this fugacity even further. The mass transfer cycle is assumed to be completed by the absorption of water vapor into transitory, flat surfaces of reduced fugacity, droplet core water exposed by collapsing droplets at the pool surface. These are assumed to be continually reforming into submerged microemulsion droplets as additional droplets collapse at the pool surface.

Analytical relationships based upon the described model allowed calculation of droplet core and sheath dimensions and droplet external interfacial tension. The efficacy of the proposed model is supported by the congruity of the thus derived values.     

Anodic Protection. Theory and Practice in the Prevention of Corrosion.: O.L. Riggs,Jr. and C.E. Locke,Plenum Press,New York, 1981, 284 pp., US$39.50.

The specific adsorption of chloride, bromide, iodide, azide, and thiocyanate has been studied at an electropolished polycrystalline silver-aqueous interface using differential capacitance measurements. For chloride, bromide, and azide, quantitative estimates of the surface concentration of specifically adsorbed anions were obtained from capacitance-potential data in mixed fluoride electrolytes having a constant ionic strength of 0.5. The dependence of the measured capacitance upon the ionic strength of sodium fluoride was also investigated in order to check the behavior of the polycrystalline surface in comparison with the predictions of conventional double-layer models. Estimates of the specifically adsorbed charge densities of chloride, bromide, and thiocyanate anions were also obtained from a “kinetic probe” technique which entailed monitoring the response of the outer-sphere reduction rate of CO(NH₃)₅F²⁺ and Co(NH₃)₆³⁺ to the addition of the appropriate adsorbing anion. At the average potential of zero charge for the polycrystalline silver surface, the standard free energies of adsorption ? Δ₃^o for chloride, bromide, and azide were found to be within ca. 5 kJ mol^?1 of the corresponding quantities obtained at mercury electrodes. However. significantly greater increases in ? Δ₃^o in the sequence Cl^? < N₃^? < Br^? are seen at silver compared to mercury. Electrochemical roughening in chloride media, giving silver surfaces displaying intense surface Raman scattering, yields only minor changes in the surface concentration of specifically adsorbed chloride anions.     

Alcohols,ethers, carbohydrates,and related compounds. IV. Carbohydrates

Ab initio calculations [B3LYP/6-311++G(2d,2p)] have been carried out on 84 conformations of 12 different sugars (hexoses), in both pyranose and furanose forms, with the idea of generating a data base for carbohydrate structural energies that may be used for developing the predictive value of molecular mechanics calculations for carbohydrates. The average value for the apparent gas phase anomeric effect for a series of 31 pairs of pyranose conformations was found to be 1.83 kcal/mol (vs. 2.67 kcal/mol with a smaller basis set used in earlier calculations). In developing MM4 to reproduce these data, it was necessary first to have good energies for simple alcohols and ethers, together with an adequate treatment of hydrogen bonding, and then to include the anomeric effect, and the ethylene glycol type system, as was previously recognized. It was also found that the so-called delta-2 effect, long recognized in carbohydrates, must be explicitly included, in order to obtain acceptable results. When a force field that included all of these items as developed from the small molecules based on the MM4 hydrocarbon force field was applied without any parameter adjustment to the set of hexopyranose and furanose conformations mentioned earlier, the E(beta) - E(alpha) was found to have an average value of 1.88 kcal/mol, versus 1.74 for the quantum calculations. The signed average and RMS deviations of the MM4 from the QM results were +0.15 and 0.87 kcal/mol.     

Vibrational spectra of dihalonitromethanes. 1. Dichloro-, difluoro-, and fluorochloronitromethanes

Conclusions Based on an analysis of the vibrational spectra of dihalodinitromethanes, it was shown that the conformation in which the NO and CH bonds are screened is predominant for dihalodinitromethanes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2523–2530, November, 1988.