Solute–solvent and solvent–solvent interactions in binary solvent mixtures. Part 8. The <TOGGLE>E</TOGGLE><INF>T</INF>(30) polarity of binary mixtures of formamides with hydroxylic solvents<FNR HREF="fn1"></FNR><FN ID="fn1">Additional material for this paper is available from the epoc website at <URL HREF="http://www.wiley.com/epoc">http://www.wiley.com/epoc</URL></FN>

Solvent effects on the binary mixtures of amides with alcohols and water were investigated by means of Reichardt's E<INF>T</INF>(30) solvatochromic indicator. E<STACK>^N<INF>T</INF></STACK> parameters of binary solvent mixtures of formamide, N-methylformamide and N,N-dimethylformamide with water, methanol, propan-2-ol, 2-methylpropan-2-ol, formamide, N-methylformamide and N,N-dimethylformamide were measured over the whole composition range of the mixtures. Application of a preferential solvation model to the solvatochromic data shows that the preferential solvation of the solvatochromic indicator by the amides decreases in the order N-methylformamide > formamide > N,N-dimethylformamide. Synergism is observed for the mixtures of the amides with alcohols of similar polarity (E<STACK>^N<INF>T</INF></STACK> value), i.e. methanol–formamide, methanol–N-methylformamide, propan-2-ol–N,N-dimethylformamide and 2-methylpropan-2-ol–N,N-dimethylformamide binary systems. Copyright © 1999 John Wiley & Sons, Ltd.