Quantum chemical study of the reaction of N,O-dimethylcarbamate with methylamine monomer and dimer

Reactions of N,O-dimethylcarbamate with methylamine monomer and dimer as a model for the polyurea preparation are studied by B3LYP and M06 quantum-chemical methods. Both a one-step interaction mechanism and a two-step route with an intermediate formed containing a tetracoordinated carbon atom are considered. The latter route is unlikely since the formation of the intermediate is characterized by small values of the equilibrium constants. Reactions involving the methylamine dimer are more favorable kinetically and thermodynamically. Kinetic preference of reactions with methylamine dimer participation is due to its increased donor and acid-base properties as compared to its monomer. The thermodynamic preference of interaction with methylamine dimer is due to a higher entropy of transformation as compared to the reaction with its monomer.