On the conformational behavior of dimethyl carbonate

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 ab initio 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.