A comparative study on vibrational, conformational and electronic structure of α,α'-diol-o-xylene, α,α'-diol-m-xylene and α,α'-diol-p-xylene.

The Fourier transform infrared (FTIR) and FT-Raman spectra of α,α'-diol-o-xylene (DOLOX), α,α'-diol-m-xylene (DOLMX) and α,α'-diol-p-xylene (DOLPX) of the configuration HOCH(2)-C(6)H(4)-CH(2)OH have been recorded in the range 4000-400 and 4000-100 cm(-1), respectively. The most stable geometry of the compounds was determined by conformational analysis. The complete vibrational assignment and analysis of the fundamental modes of the most stable conformer of the compounds were carried out using the experimental FTIR and FT-Raman data and quantum chemical studies. The observed vibrational frequencies were compared with the wavenumbers derived theoretically for the optimised geometry of the compounds from the DFT-B3LYP gradient calculations employing the standard 6-31G** and high level and 6-311++G** basis sets. The structural parameters and vibrational wavenumbers obtained from the DFT method are in good agreement with the experimental data. The potential energy distributions of the fundamental modes were also calculated by Wilson's FG matrix method. The effect of -CH(2)OH groups on the skeletal vibrations have been discussed. The intra molecular n→σ* and π→π* interactions were discussed with NBO analysis.