Urea methanolysis mechanism: a computational study

Theoretical study of the reactions of urea with methanol with the formation of O-methyl carbamate and reactions of O-methyl carbamate with methanol with the formation of dimethyl carbonate by the B3LYP and M06 methods has shown that these transformations can proceed according to the concert mechanism. Reactions involving methanol monomers cannot be real pathways for the formation of reaction products. In both transformations, reactions involving linear methanol dimers and trimers are kinetically and thermodynamically more preferable than reactions with methanol monomers. The stage that determines the rate of formation of dimethyl carbonate is the interaction of O-methyl carbamate with methanol associates. The interactions of urea with methanol associates with the formation of O-methylcarbamate are almost irreversible. However, the reactions of O-methylcarbamate with methanol associates with the formation of dimethyl carbonate are substantially reversible. This requires the use of measures to shift the equilibrium towards the reaction products in this interaction.