Probing solid-state reaction mechanisms with THz-TDS

Terahertz radiation is used to follow the solid state reaction to form cocrystals of theobromine and oxalic acid. The formation of an intermediate state is observed, and the cocrystal formation kinetics display a different reaction profile to the loss of the intermediate, thus supporting a moisture mediated reaction mechanism. We propose that THz-TDS is a useful tool in understanding such reactions, and by extension a research aid to understanding solid-state mechanisms and advancing green chemistry concerns.