Temperature dependence of the Hammett reaction constant

Abstract

The temperature dependence of the Hammett reaction constant, ρ, for the hydrogen-exchange reactions of various substituted NN-dimethylanilines has been examined over the temperature range 25–96 °C. Empirical and semi-empirical evidence predicts that ρ should be a linear function of T^–1, but the experimental data are equally well correlated by five other arbitrarily selected functions of temperature (T;T^½, T², T^–2, and ln T). Thus a sufficient range in ρ value has yet to be attained to unequivocally confirm that ρ is a function of T^–1.