Infrared Spectra of Methanol and Deuterated Methanols in Gas, Liquid, and Solid Phases

Abstract

The infrared spectra of CH3OH, CH3OD, CD3OH, and CD3OD in the five phases gas, liquid, vitreous solid, α-crystal, and (except perhaps for CD3OH and CD3OD for which the solid-solid transitions have not been studied) β-crystal have been recorded in the range 4000 to 300 cm−1. The Raman spectrum of liquid CD3OH has been recorded. A complete assignment of the internal modes is given, which differs somewhat from previous assignments for the CH3 bending and rocking vibrations. No significant difference in spectrum occurred between the α-crystal and β-crystal phases. Under the full symmetry of the β-phase determined by x-ray diffraction only one OH out-of-plane bending band should occur. Two bands are observed, and it is concluded that the carbon and oxygen atoms in one chain are not coplanar, as is required by the symmetry determined by x-ray diffraction [K. J. Tauer and W. N. Lipscomb, Acta Cryst. 5, 606 (1952)], but that the chains are puckered and the x-ray symmetry arises because the puckered chains are irregularly distributed, a structure that had been previously suggested by Tauer and Lipscomb tentatively on the basis of high apparent thermal amplitudes. Bands occur in the crystal spectra near 500 cm−1 and 340 cm−1 at −180°C. These are interpreted as lattice modes, probably the two infrared-active modes that involve translations of the molecules.