The potential function for the internal rotation and the derived potential energy distribution of the normal modes for 3-chloropropionyl chloride based on ab initio calculations

The conformational behavior and structure of 3-chloropropionyl chloride were investigated by ab initio calculations. The 6311++G(**) basis set was employed to include polarization and diffuse functions in the calculations at RHF and MP2 levels. The compound was predicted to exist as a complex mixture of stable conformers. The trans-cis conformation with minimum chlorine- chlorine interaction was predicted to be the lowest energy form for the molecule. From the potential scan, the barrier for internal rotation between the trans-cis and trans-gauche conformers was calculated. The vibrational frequencies were computed at the HF level. Normal coordinate calculations were carried out and potential energy distributions among symmetry coordinates were calculated for the stable conformers of the molecule. Raman and infrared spectra of both the individual conformers and the mixture of them were computed at 300 K.