SOLUTE-SOLVENT INTERACTIONS IN AMIDE-WATER MIXED-SOLVENTS

Excess volumes, mixing viscosities, and excess Gibbs energies of activ ation of viscous flow of the aqueous binary mixtures of the amides for mamide, N-methylformamide, N,N-dimethylformamide, pyrrolidin-2-one, an d N-methyl-2-pyrrolidinone were calculated from density and viscosity measurements. The values of these functions point to strong amide-wate r interactions with formation of a variety of aggregates, the nature o f which depends on the extent of substitution of the amides; compariso n of the functions of the same amides with alkan-1-ols reveal an impor tant hydration effect. Various one-parameter and two-parameter empiric al models for prediction of mixing viscosities were in good agreement with the experimental results only for the formamide-water system; non e of the models predicted satisfactorily the behavior for the aqueous mixtures of both mono-and disubstituted amides.