Cross enthalpic pair interaction coefficients with water in N,N-dimethylformamide and with N,N-dimethylformamide in water

Abstract

From earlier published enthalpies of solution of various organic compounds in binary solvent systems containing water and N,N-dimethylformamide (DMF), the enthalpic pair interaction coefficients (B^h_xy) of these compounds with DMF in water as solvent, and with water in DMF as solvent have been evaluated. The organic solutes comprise urea, alkylsubstituted ureas, amides and alkanols. For water dissolved in DMF, enthalpic interaction coefficients have been obtained from microcalorimetrical dilution experiments. In water and DMF the various results differ considerably. In water a much larger variation in B^h_xy is found than in DMF. In the former an almost constant CH₂ contribution to B^h_x,DMF is found for most homologous series. Branching of the alkyl chain in the organic compound hardly influences B^h_x,DMF. The results indicate that hydrophobic interaction plays an important role. In DMF the results are less regular and branching effects are considerable. Hydrogen bonding has a large impact on B^h_x,H2O. The relations between the enthalpic pair interaction coefficients on basis of the Savage and Wood additivity approach and the Barone method (square root rule) are tested. When sufficient functional groups are introduced, the Savage and Wood concept seems to work well for a large amount of molecules of different classes in water. The Barone approach seems to be more useful for the interaction between molecules with comparable functional groups.