KINETIC AND THERMODYNAMIC STUDY OF 2-BROMO-2-METHYLBUTANE, 2-CHLORO-2-METHYLBUTANE AND 3-CHLORO-3-METHYLPENTANE IN DIOLS

Rate constants, k, were determined for the solvolytic reactions of 2-b romo-2-methylbutane, 2-chloro-2-methylbutane and 3-chloro-3-methylpent ane in 10 pure diols at 298.15 K. The Gibbs energies of activation wer e calculated in order to study the influence of the solvent and to pro vide mechanistic information about the activation process. By combinin g these values with a set of infinite dilution activity coefficients, gamma(infinity), the transfer Gibbs energies of the reactants (initial state) and of the activated complex (transition state) were obtained, which allowed the solvent effects on both states to be quantitatively analysed. The gamma(infinity) values were calculated using the UNIFAC group contribution method. The modified Flory-Huggins equation was us ed in the combinatorial term. The interaction parameters were taken fr om the specific UNIFAC gamma(infinity) interaction parameter table, ex cept for the gamma(infinity) values of 2-chloro-2-methylbutane and 3-c hloro-3-methylpentane in diethylene glycol and triethylene glycol, whi ch were obtained using the gamma(infinity) UNIFAC-VLE interaction para meter tables. For comparative purposes all the ether infinite dilution activity coefficients of the three solutes in the diols were also cal culated using the UNIFAC-VLE parameter tables. (C) 1998 John Wiley & S ons, Ltd.