Substitution in polymethylbenzenes. Part XXIII. Arrhenius parameters for the chlorination of polymethylbenzenes in 1 : 1 acetic acid–propionic acid mixture

Abstract

Energies and entropies of activation for the chlorination of some polymethylbenzenes in a 1 : 1 acetic acid–propionic acid mixture containing 2% of water have been determined. This mixed solvent, since it makes possible rate studies over a much larger temperature range than acetic acid, appears very convenient for the determination of Arrhenius parameters for the chlorination of very reactive substrates. The results have shown that along the whole series of methylbenzenes the entropy of activation remains nearly constant: any change in the rate of chlorination appears to be determined essentially by changes in the energy of activation. Some implications are briefly discussed.