Quantum-chemical study of the stability of solvents with respect to strong organic bases

Abstract

The possibility of theoretical calculation of the ionization constants of strong organic bases in dimethyl sulfoxide and hexametapole was studied by the DLPNO-CCSD (T) and DFT methods. By comparison with the experimental data available in the literature, it has been established that the error of such calculations lies within 1–2 pKa units. The stability of some ionizing solvents against strong organic bases is investigated, the mechanisms of decomposition of solvent molecules in strongly basic media are predicted, and the corresponding energy barriers are estimated. According to the calculations, among ionizing solvents, hexamethylphosphoramide has the highest resistance to superbases, being able to maintain pH > 50 at room temperature. At the same time, 1,3-dimethyl-2-imidazolidinone gradually decomposes under these conditions, while tetrahydrofuran and pivalonitrile are even less stable.