Computational study of the thermodynamics of urea methanolysis

Enthalpies, entropies, Gibbs free reactions of the interaction of urea and carbamic acid methyl ester with a monomer, dimer and trimer of methanol to form, respectively, carbamic acid methyl ester and dimethyl carbonate were determined using B3LYP and M06 density functional methods with the 6–311++G(df, p) basis set. Both of the quantum chemical methods used lead to comparable results. The enthalpies and entropies of transformations increase with an increase in the degree of association of alcohol. Changes in the free energies of the reactions discussed are controlled by the entropy term, which leads to the thermodynamic preference for reactions involving methanol complexes compared to its monomer.