Raman spectra of methanol-water mixtures were measured over the whole composition range at room conditions. The spectra are used to quantify the strength of intermolecular interactions in terms of local internal pressures. The conclusions derived from the spectroscopic analysis are discussed within the framework of the solvation pressure model using values of the cohesion energy density expected in the mixture. This work demonstrates that an appropriate analysis of Raman spectroscopy experiments can be used to quantify the local internal pressures due to intermolecular interactions in liquid mixtures, provided that high pressure results of the pure liquids are available.

Raman spectra of 1,2-ethylenediamine (EDA) in aqueous solutions are used to demonstrate that EDA molecules experience an anti-gauche conformational change resulting from the interactions with water. The observed Raman shift reveals a compressive (hydrophobic) effect of water on both methylene and amino groups of EDA. Raman spectra of EDA at high pressures are used as reference to quantify the intermolecular EDA-HO interactions in terms of local pressures. These results are compared with macroscopic solvation pressures calculated from the cohesive energy parameter. We compare and discuss all our observations with available computational and experimental studies.