Theoretical gas phase study of the gauche and trans conformers of 1-bromo-2-chloroethane and solvent effects

Abstract

This is a systematic gas phase study of the gauche and trans conformers of 1-bromo-2-chloroethane. The methods used are second order Møller-Plesset theory (MP2) and density functional theory (DFT). The basis set used is 6-311++G(d,p) for all atoms. The functional used for DFT method is B3LYP. G2/MP2 and CCSD(T) calculations have also been carried out using MP2 optimised structure. The results indicate that there is more preference for the trans conformer. The energy difference between the trans and gauche conformers (ΔEtg) and related rotational thermodynamics are reported. The MP2/6-311++G(d,p) energy difference (ΔEtg) for 1 -bromo-2-chloroethane is 7.08 kJ/mol. The conformers of 1 -bromo-2-chloroethane have also been subjected to vibrational analysis. This study has also been extended to investigate solvent effects using the Self-Consistent Reaction Field methods. The structures of the conformers are not much affected by the solvents but the energy difference (ΔEtg) decreases with increasing polarity of the solvent. The results from the different theoretical methods are in good agreement. © Springer-Verlag Berlin Heidelberg 2007.