The density functional theory and MP2 method were employed to study the reaction pathways of methanolysis of 3-methyl cyclic ethylene phosphate (MEP): (I) CH3O－＋MEP; (II) CH3OH＋MEP; (III) CH3O－＋HMEP (protonated form of MEP); (IV) CH3OH＋HMEP. The geometries for the reactants, intermediates, transition states and products were optimized at B3LYP/6-31＋＋G(d,p) level, and the natural charge was analyzed at the same level. The single point energy of each stationary point was calculated at MP2/6-311＋＋G(3df,2p) level. The effect of various solvents such as benzene, methanol and water on the reaction pathways was assessed by the polarizable continuum model. The calculated results show that the solvent effects reduce the free energy barrier for pathway I, while increase the free energy barriers for rate-controlling step of pathways II and IV. Pathway IV is the most favorable one in the gas phase and benzene, while pathway I becomes the most favorable one in both methanol and water. Our calculated results also indicate that the pathways II and IV contribute to the total reaction equally under the experimental condition.

Key words: 3-methyl cyclic ethylene phosphate, methanolysis, reaction pathway, solvent effect