Computational prediction of the spectroscopic parameters of methanediol, an elusive molecule for interstellar detection

Abstract

The molecular structure of methanediol has been investigated by means of quantum chemical calculations. Two conformers, corresponding to C2 and Cs symmetries, respectively, were considered. The C2 conformer is found to lie about 1.7 (at 298 K) or 2.3 (at 0 K) kcal mol−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 Cs conformer has a relatively high dipole moment, namely, 2.7 D. The barrier for the Cs→C2 process is predicted to be around 0.7–1 kcal mol−1. Based on the energetic results the proportion of the Cs 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.