Kinetic studies of hydrogen exchange in substituted dialkylanilines. Part III. Thermodynamic relationships of exchange

Abstract

Hydrogen exchange data for NN-dimethylaniline and fourteen nuclear-substituted NN-dimethylanilines are recorded. Activation free energies conform to a Hammett-type substituent relationship when using σ⁺-values. Resolution of the measured enthalpy changes into external and internal components leads to a satisfactory interpretation of the linear free energy relation. External enthalpy changes are almost entirely compensated by entropy changes, and this is discussed in terms of solvent–solute interaction.