Browsing by Author "Chaudhri, Shamim A."

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    Dissociation Equilibrium of Nitroform in Mixtures of Polar Solvents Studied by Pulse Radiolysis
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (6), 1972) Chaudhri, Shamim A.; Asmus, K. D.
    The dissociation equilibrium C(NO2)3H ; C(NO)2,+H sol and the related kinetics have been studied for mixtures of polar solvents. The dissociation constant is found to be essentially controlled by the rate constant for the neutralization of nitroform anions by solvated protons. An almost linear dependence of the pK of nitroform on the solvent composition is observed for t-butanol- ethylene glycol mixtures. With water as one of the solvent components, a different effect on the dissociation constant is noted and the pK value rapidly attains that for pure water. In mixtures of acetone and alcohols the pK against solvent composition curve goes through a minimum. The results arc discussed on the basis of the neutralization kinetics of the nitroform anion.
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    Dissociation Equilibrium of Nitroform in Polar Solvents Studied by Pulse Radiolysis
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (3), 1972) Chaudhri, Shamim A.; Asmus, K. D.
    The dissociation equilibrium C(NO2)3H --- C(NO2)3+Hsol and the related kinetics have been studied for various solvents (alcohols, acetone, and water) by means of pulse radiolysis. Nitroform anions were produced by radiation-chemical reduction of tetranitromethane which was dissolved in these liquids. The dissociation constant K of nitroform decreases with decreasing dielectric constant; its value ranges from 6.3 x 10-1 M for water to 2.5 x 10-7 M for t-butanol. K is essentially controlled by the rate constant kn for the neutralization of C(NO2)3 by solvated protons (3.4 x 104 M-1 s-1 in water and 5.0 x 109 M-1 s-1 in t-butanol), while the rate of dissociation of C(NO2)3H depends relatively little on the nature of the solvent. A linear relationship has been found between log kn and log A'. Nitroform anions arc also neutralized by proton transfer from solvent molecules. The rate constant for this process does not vary much with the properties of the solvent. Equivalent conductivities for C(NO2)3 + Hsol ion pairs have also been determined.