Nuclear magnetic resonance spin–lattice relaxation studies of H3O+ and —CH3 group reorientations in para-toluenesulphonic acid hydrate

Abstract

Proton spin–lattice relaxation times have been studied in para-toluenesulphonic acid hydrate, CH₃C₆H₄SO₃^–H₃O⁺, as a function of temperature between 80 K and its melting point. Two relaxation processes occur which have been attributed to three-fold reorientations of the oxonium ion, H₃O⁺, and the methyl group, —CH₃. Activation energies of 51.6 and 7.30 kJ mol^–1, respectively, have been determined for these processes and they are discussed in terms of the interactions of the rotors with their environment in the lattice.