Theoretical mechanism for the oxidation of thiourea by hydrogen peroxide in gas state

This article presents a theoretical reaction mechanism for the oxidation of thiourea by hydrogen peroxide using density functional theory and ab initio methods. This work also focuses on the analysis of the potential energy surface (PES), thermodynamic and kinetic properties for the designed oxidation mechanism of thiourea using BH&HLYP and B3LYP methods. Both DFT calculations lead to similar reaction paths. The results of the thermodynamic analysis for the designed oxidation mechanism of thiourea are reasonable and feasible. Based on the research on the activity energies, activity enthalpies and activity Gibbs free energies obtained from the determined reaction pathways, we conclude that the oxidation of thiourea by hydrogen peroxide in vacuum was well completed. Because the active relative energies, the relative enthalpies and the relative Gibbs free energies of Reaction 4 predicted by Path II are higher than those predicted by Path I. Kinetics calculations suggest that the designed Path I is more favorable than Path II. The basis sets and calculation methods have strong effects on the thermodynamics and kinetics calculations.