On the conformational behavior of dimethyl carbonate

Abstract

Infrared (4000–50 cm^-1) spectra of the vapor, the amorphous and crystalline solid phase, and Raman spectra (4000–50 cm^-1) of the vapor, liquid and crystalline solid phases of dimethyl carbonate have been recorded, and assignments are proposed. MP2 and DFT abinitio calculations were carried out using a 6-31G** basis set. The calculations show that the compound can occur as the cis–cis, cis–trans and near-trans–near-trans conformers, with the cis–cis being the global minimum. Vibrational frequencies and solvation free enthalpies were predicted on the DFT level of theory. Both cis–cis and cis–trans conformers were identified in the vibrational spectra of all fluid phases. The enthalpy difference between them was determined to be 8.0(4) kJ mol^-1 in the pure liquid phase and 13.6(9) kJ mol^-1 in the vapor phase.