EXCESS MOLAR VOLUMES FOR N,N-DIMETHYLACETAMIDE PLUS WATER AT 25-DEGREES-C

Densities have been measured for the system N,N-dimethylacetamide (DMA) + water at 25 degrees C. The values have been converted to excess molar volumes. The values for water-rich mixtures were found to agree well with the more sparse results given in earlier publications. For equimolar and amide-rich mixtures the additional, measurements reported here complement the previous results. The present measurements seem to confirm an earlier observation that the value of the apparent molar volume of DMA, at infinite dilution in water, is significantly lower than would be predicted on the basis of a simple group additivity scheme. The results of some molecular modeling computations of various small amides seem to support the suggestion that DMA is a particularly crowded molecule.