Infrared study of hydrogen bonding of methanol in the liquid phase

Abstract

The V(_s)(OH) band of methanol in binary system has been studied by using infrared spectroscopy, over the whole concentration range between 0.01 - 0.7 methanol mole fraction. The aim of this study is to analyze this band which is very complicated, due to overlapping between its band components, and to correlate the results to the possible underlying equilibrium. Also the change in the V(_s)(OE) band shape across the concentration range, imposed the necessity of studying the V(-s)(OH) of methanol in non-polar solvent at a very low concentrations (0.0049 to 0.0246 mol/dm(^3)) in order to identify the existing varieties of methanol hydrogen bonded species, as well as the monomer. A study of the V(_s)(OH) for methanol in the ternary system (CH(_3)OH/CH(_3)CN/CCL(_4)) was undertaken, in order to defferentiate the band components of the hydrogen bonded complexes formed from methanol and acetonitrile molecules, from the hydrogen bonded methanol aggregates. This study was carried out in a concentration range of 0.0044 to 0.0177 mol/dm(^3). For the binary system, because of the complexes of the bands, a band fitting programs were used as a means of estimating the number of bands present, their positions and band shapes of each component. As a result, this study has shown that the I.R. data for methanol in acetonitrile band fitting model contained: monomer, dimer, 1:1 and 2:1 complexes, trimer, tetramer and pentamer species.