Molecular structures of gauche and anti conformers for oxalyl bromide: ab initio and DFT calculations

The molecular structure and conformational nature of oxalyl bromide are investigated by the ab initio and DFT methods. Both the MP2 and B3LYP optimized structures are better consistent with the experimental result in the gas phase. The CC bond torsional angle of the gauche conformation is quite sensitive to the choice of the calculational level. The B3LYP potential energy surface around the anti conformation is so flat that the existence of the anti conformation is not certain. It is suggested that the geometry calculations at the MP2 level can explain the nature of conformation in oxalyl bromide better than those at the B3LYP level.