OPTICAL AND CALORIMETRIC STUDIES ON THE ROLE OF LATTICE MODE SOFTENING IN ASSISTING A THERMALLY ENHANCED SOLID-STATE REACTION

The concept of phonon-assisted solid-state chemical reactions is analy zed in the case of the thermal rearrangement of methyl p-dimethylamino benzenesulfonate (MSE) to a zwitterionic product p-trimethylammoniumbe nzenesulfonate. The experimental Raman scattering reinvestigation of M SE as a function of temperature shows that mode softening does not pla y an important role in the thermal reaction of MSE. A series of struct ural phase transitions in the [90-300 K] temperature range is shown in the MSE crystal by calorimetry, infrared absorption and Raman scatter ing.