Theoretical study of proton transfer and tautomerization mechanisem in trithiocyanuric acid in the presence of water and methanole clusters

In this research, the thion-thiol tautomerism of trithiocyanuric (TCA) acid has been studied using B3LYP methods with 6-311++G(d,p) and 6-311++G(2d,2p) basis sets. Trithiocyanuric acid (TCA), with three proton transfer steps, becomes to the final product (TCA4) containing three thiol bonds. In order to study the effect of structure and number of solvent molecules on potential energy surfaces, all three proton steps evaluated in the presence of one and two water or methanol molecules. Results indicated that three proton transfer processes are endothermic both in gas phase and in the presence of solvent molecules. So, the thion forms (reactants) are more stable than the thiol forms (products). Also, the first step proton transfer is the most unfavorable both dynamically and thermodynamically. The stabilization energy of all complexes and the energy barrier are reduced significantly in the presence of solvent molecules. In all cases, TCA1 is the most stable one in all reactants and products' structure. Overall proton transfer process is an endothermic and none-spontaneous process producing an unstable structure (TCA4)