Theoretical and experimental mechanistic study of water molecule involvement in the Prilezhaev reaction

The Prilezhaev reaction produces epoxides using alkenes and peroxy acids such as m -chloroperoxybenzoic acid ( m CPBA). The reaction proceeds via a concerted mechanism in one step. Although the m CPBA used in organic syntheses contains water because of its explosive nature, the effects of water on the reaction have not been considered. To investigate the effects of water on the reaction mechanism, we determined the thermodynamic parameters for the Prilezhaev reaction between styrene and m CPBA. The activation free energies, including solvent effects, were calculated using the SMD and QM/MC/FEP methods. The calculated thermodynamic parameters for the reaction directly involving two water molecules were in better agreement with the experimental data than those for the concerted mechanism. This result indicated that water molecules are involved in the progression of the m CPBA-mediated Prilezhaev reaction in solvents containing water molecules. Based on the good agreement between the measurements in the presence of water and the calculations of our proposed reaction mechanism, we have shown that water in the solvent plays a significant role in the formation of the epoxide ring.