The interaction between aromatic rings and sulfur atoms in the side chains of amino acids is a factor in the formation and stabilization of alpha-helices in proteins. We studied the H(2)S-benzene dimer as the simplest possible prototype of sulfur-pi interactions. High-quality potential energy curves were obtained using coupled-cluster theory with single, double, and perturbative triple substitutions (CCSD(T)) and a large, augmented quadruple-zeta basis set (aug-cc-pVQZ). The equilibrium intermonomer distance for the hydrogens-down C(2)(v) configuration is 3.8 A with an interaction energy of -2.74 kcal mol(-1). Extrapolating the binding energy to the complete basis set limit gives -2.81 kcal mol(-1). This binding energy is comparable to that of H(2)O-benzene or of the benzene dimer, and the equilibrium distance is in close agreement with experiment. Other orientations of the dimer were also considered at less complete levels of theory. A considerable reduction in binding for the sulfur-down configuration, together with an energy decomposition analysis, indicates that the attraction in H(2)S-benzene is best thought of as arising from a favorable electrostatic interaction between partially positive hydrogens in H(2)S with the negatively charged pi-cloud of the benzene.

A route to explain water anomalies from results on an aqueous solution of salt Salt effects on the surface tensions of dilute electrolyte solutions: The influence of nonzero relative solubility of the salt between the coexisting phases J. Chem. Phys. 80, 6225 (1984); 10.1063/1.446725The solubility of some sparingly soluble lead salts: An evaluation of the solubility in water and aqueous electrolyte solutionThe literature on the solubility of mercury and of the sparingly soluble salts of mercury-(I) and mercury (II) in water and in aqueous electrolyte solutions has been reviewed. The solubility data have been compiled and evaluated. Recommended and tentative values of Jh_e solul?Aiti es are preseI.1t¢ when warranted. AuxiliafY'thermodynamic data and crystallographic data useful in the interpretation of solubility data are given. An annotated bibliography on the solubility of some of the less common inorganic mercury compounds, with emphasis on the solubility literature published since 1950, is given.

A route to explain water anomalies from results on an aqueous solution of salt Salt effects on the surface tensions of dilute electrolyte solutions: The influence of nonzero relative solubility of the salt between the coexisting phases J. Chem. Phys. 80, 6225 (1984); 10.1063/1.446725The solubility of some sparingly soluble lead salts: An evaluation of the solubility in water and aqueous electrolyte solutionThe literature on the solubility of the sparingly soluble inorganic salts of zinc and cadmium in water and in aqueous electrolyte solutions has been reviewed. The solubility data have been compiled and evaluated. Recommended or tentative values of the solubilities and the solubility products have been given when warranted. Auxiliary thermodynamic and crystallographic data useful in the interpretation of solubility data are given. For the many zinc and cadmium substances for which only limited solubility. data are available, unevaluated values are given in an annotated bibliography with emphasis on solubility data published since 1950.

Physical chemistry is commonly viewed as formidable by chemistry faculty and students alike. It is the gateway course to advanced chemistry courses in ACS-certified degree programs. Hypotheses concerning success in physical chemistry based on previous chemistry, physics, and mathematics courses are tested using bivariate correlation analysis, multiple regression on the full set of variables, and multiple regression with a subset of variables deleted. Data on chemistry, physics, and mathematics grades and the number of times these courses were repeated were collected for physical chemistry students at Valdosta State University for the period 1976–1999. The most important subsets of variables were chemistry and mathematics. The most important individual predictors of success in the first course in physical chemistry are grade in second course in organic chemistry and grade in physics. The number of times courses were repeated is important but less significant.

Ethyne was probably first made in the laboratory by Edmund Davy in 1836. It was rediscovered nearly a quarter of a century later by Berthelot who gave it the name acetylene. Since that time ethyne has become a cheap raw material for the synthesis of organic materials and an important industrial fuel. A summary of the available solubility data for ethyne was published by Miller in 1965 [S. A Miller, Acetylene—Its Properties, Manufacture, and Uses (Academic, New York, 1965), Vol. I]. Many more data are now available in a wide range of research papers and patent applications. These data vary in their reliability. In the current work the data for systems included in Miller’s book have been reassessed and complemented by data published more recently. Literature has been surveyed to 1999. Data for a system may be unreliable unless two or more groups of workers have published values in close agreement. Where possible values of the mole fraction solubility at a partial pressure of 101.3 kPa have been tabulated. Equations have been given for the variation of mole fraction with temperature in cases in which values over a temperature range are available. The greater the number of independent sources of the data the more the reliance which can be placed on the utility of the resulting equation. Extrapolation of such equations beyond the temperature range of experimental measurements can lead to errors. In many of the systems it may be assumed that approximate values of the mole fraction solubility, x1, at a partial pressure of 101.3 kPa may be obtained by linear extrapolation of values for lower partial pressures, p1, on the assumption that x1/p1 is approximately constant. However a similar linear extrapolation of solubilities at pressures appreciably higher that 101.3 kPa to give mole fraction solubilities at 101.3 kPa can lead to gross errors. For the purpose of evaluation of data use has been made of the Krichevsky–Il’inskaya equation to obtain approximate values of solubilities at 101.3 kPa from measurements at higher pressures. These values were then compared with measurements made at or near to 101.3 kPa.