Selective molecular interactions between dimethyl sulfoxide and the functional groups of 2-mercaptoethanol

With the help of excess infrared spectroscopy, a modified component-normalization method in two-dimensional correlation spectroscopy has been proposed for investigating molecular interactions. In this method, deviation of absorption coefficient of a concerned component in mixtures from that of its pure state is expressed as the value of excess molar absorbance divided by the mole fraction of the concerned component. Compared with the original component-normalization method, the new method can reduce the influences from non-concerned components. Using the new data pretreatment method, selective hydrogen bonding interactions between dimethyl sulfoxide (DMSO) and the two functional groups (OH and SH) of 2-mercaptoethanol (ME) were studied by two-dimensional infrared correlation spectroscopy. The results show that, although both OH and SH groups in ME can interact with DMSO, DMSO molecule interacts selectively with the OH group of ME molecule at low concentrations of DMSO. Results of excess infrared spectroscopy also support the conclusion.