COMPUTATIONAL PREDICTION OF THE SPECTROSCOPIC PARAMETERS OF METHANEDIOL, AN ELUSIVE MOLECULE FOR INTERSTELLAR DETECTION

The molecular structure of methanediol has been investigated by means of quantum chemical calculations. Two conformers, corresponding to C sub(2) and Cs symmetries, respectively, were considered. The C sub(2) conformer is found to lie about 1.7 (at 298 K) or 2.3 (at 0 K) kcal mol super(-1) below the Cs conformer. Predictions for their rotational constants, vibrational frequencies, IR intensities, and dipole moments have been provided. The lowest-lying isomer has a very low dipole moment, around 0.03 D, whereas the C sub(v) conformer has a relatively high dipole moment, namely, 2.7 D. The barrier for the Cs[arrowright] C sub(2) process is predicted to be around 0.7-1 kcal mol super(-1). Based on the energetic results the proportion of the C sub(s) conformer is likely to be negligible under low temperature conditions, such as in the interstellar medium. Therefore, it is predicted that detection by radioastronomy of methanediol would be rather unlikely.