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The factors affecting the methanolysis of polycarbonates catalyzed by sodium methylate are studied. The conversion rate increases with an increase in the basic properties of solvents; the rate of methanolysis depending on the amount of solvent (tetrahydrofuran) is described by an extreme dependence. Changes in sodium methylate concentration and temperature have a small effect on the methanolysis of polycarbonates.

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.

The mechanism of N-methylformamide metathesis with dimethyl carbonate, which leads to the formation of N,O-dimethyl carbamate, is studied using the quantum-chemical B3LYP/6-311++G(df,p) approach. The reaction consists of three stages: the conversion of formamide to iminol; the adding of dimethyl carbonate at the azomethine bond of iminol; and decomposition of the resulting product into carbamate and methyl formate. The second stage limits the rate of interaction. All stages proceed through concerted cyclic transition state, and all of them are catalyzed efficiently by a monomer and a dimer of methanol.

The mechanisms of noncatalytic and autocatalytic addition–elimination reactions of dimethyl carbonate with methylamine have been studied in terms of wB97XD/6-311++G(df,p), M06/6-311++G(df,p), and PBE0/6-311++G(df,p) quantum chemical methods, and thermodynamic and activation parameters of these reactions have been calculated. The rate-determining stage is the formation of tetrahedral carbon intermediate. The addition–elimination mechanism is preferred over the autocatalytic SN2 mechanism determined by enhanced donor–acceptor and acid–base properties of amine complexes with alcohol associates in comparison to amines.

The B3LYP/6-311++G(df,p) quantum-chemical simulation has revealed that linear associates of methanol catalyze the ketone–enol, nitro–aci-nitro, and carbamate–azomethinenol tautomeric transformations. All the reactions proceed via the coherent transition states. The catalytic effect is enhanced with the increased alcohol degree of association. The acid-base properties of methanol are changed similarly.

The mechanism of transformation of 2-hydroxyethyl carbamate into ethylene carbonate was studied at the DFT B3LYP and M06 levels of theory. The reactions proceed through pre- and post-reaction complexes and cyclic transition states. The free energy barrier decreases when ethylene glycol molecule or zinc oxide is involved.