The Structure of Water and Solute-Solvent Interactions in Aqueous Solutions （Part 2） : Solute-Solvent Interaction

The influences of various solute molecules upon the structure of water have been investigated by means of the ultrasonic pulse technique. It is shown that typical protein denaturants such as urea and guanidine hydrochloride behave as a structure breaker of the water structure. This effect of the denaturants is closely related to the denaturing process of protein molecules in water. The effects of alkyl-substituted ureas upon the water structure have been studied in order to obtain information on hydrocarbon-water interactions. 1,3-Dimethylurea molecules behave as a weak structure breaker, but 1,3-diethylurea molecules behave as a structure former in water. The solute-solvent interactions in aqueous solutions of tetramethylurea are essentially similar to that of 1, 3-dimethylurea solutions in low concentrations. The behavior of several neutral amino acids in water is similar to each other, irrespective of their difference of size of alkyl groups contained in solute molecules. It is said that neutral amino acids can not be used as a model for studying the iceberg formation. In the case of aqueous diamine solutions, the iceberg formation around hydrocarbon groups become appreciable at the carbon number 3 in solute molecules.It is concluded that the structure of icebergs formed in dimine solutions is more dense and stable than that of the ice-like structure in bulk water