Vibrational spectra and assignments of 1-bromo-2-iodoethane

Infrared absorption and Raman spectra of liquid 1-bromo-2-iodoethane and 1-bromo-2-iodoethane in different solvents were taken. Additional infrared absorption and Raman spectra were obtained for solid 1-bromo-2-iodoethane. Ab initio vibrational frequencies of the anti and gauche conformers have been calculated at the RHF/3-21G* level of theory by using the point group symmetries of C-1 and C-S, respectively. Vibrational frequency assignments for seventeen infrared and Raman active modes have been determined for both anti and gauche conformers. The experimental data and the ab initio calculations indicate that the anti conformer is more stable than the gauche conformer, The Raman intensities of the C-l stretch bands as a function of temperature were used to obtain the change of enthalpy between the anti and gauche conformers. The experimentally determined enthalpy difference between the anti and gauche conformers was found to be Delta H = 4.81 +/- 0.21 kJ/mol for neat liquid 1-bromo-2-iodoethane. (C) 1998 Elsevier Science B.V. All rights reserved.