Energetics of the non-covalent interactions in the acetonechloroform system by MP2/CBS quantum chemical calculations

Abstract We studied the energetics of the non-covalent interactions present in the acetone-chloroform system at the MP2/Complete Basis Set level of theory to shed light on the interactions responsible for azeotrope formation. To this end, we did a configurational search for the diverse geometries of homodimers of (acetone)2 and (chloroform)2 , and acetone-chloroform heterodimers. All the structures were subjected to full geometry optimization and their vibrational frequencies calculated. Energies were extrapolated to the Complete Basis Set limit and BSSE correction applied. We found that MP2/Complete Basis Set level of theory predicts the trend (acetone)2 > acetone-chloroform > (chloroform)2 , while MP2/cc-pVDZ severely underestimates the interaction energies as well as predicts a wrong trend in the energies. The resulting wavefunctions were analyzed by Reduced Density Gradient and Non-Covalent Interaction methods yielding a variety of critical points. This revealed that the reported hydrogen bond for the acetone-chloroform dimer likely has a van der Waals component involving interaction between a chlorine in chloroform and a hydrogen in acetone.