Fourier transform Raman spectrum, vibrational assignment and ab initio calculation of methanesulfonic acid in the gas and liquid phases

The Fourier transform Raman spectrum of liquid methanesulfonic acid, CH3SO2 OH, was recorded and the spectral data were interpreted in detail. Ab initi o calculations were carried out with different basis sets up to MP2/6-311+G (2d,2p), from which structural parameters and conformational stabilities me re determined. The spectrum of the liquid is interpreted on the basis of a dimer structure with C-i symmetry. Normal coordinate calculations were carr ied out for both the monomer and dimer and the results indicate that the di fferences in wavenumbers for the normal vibrations for the monomer and dime r are relatively small. These calculations also indicate that the dimer str ucture is a reasonable model for the associated molecules of methanesulfoni c acid in the liquid phase. The spectroscopic and theoretical results are c ompared with the corresponding quantities for some similar molecules. Copyr ight (C) 2000 John Wiley & Sons, Ltd.