Detection of water–polar solvent interaction using melting of a eutectic

We focused on the eutectics of water and a lower alcohol or polar solvent, and investigated the relationship between the change in the solution structure and the melting peak of the eutectic in aqueous solutions of ethanol, propanol or DMSO. We found that the melting temperature and melting enthalpy of 0.05 alcohol molar fraction solutions were almost constant regardless of ultrasonic treatment, while the melting enthalpy of 0.10 alcohol molar fraction solutions fell to 81% (ethanol) and 46% (1-propanol) of the pretreatment value. The melting enthalpy of the eutectic of a polar solvent and water may be reduced by ultrasonic treatment in the liquid state. These results agree with the data from 17O NMR of water and the absorption peak at 1150 nm for free water. These results show that water–polar solvent interaction can be detected by examining the melting of a eutectic of a polar solvent and water using sensitive DSC.