Static dielectric constants of the binary mixtures of N-methylformamide with water, ethyl alcohol, ethylene glycol, dimethylsulphoxide, acetone and 1,4-dioxane

The static dielectric constants of binary mixtures of N-methylformamide (NMF), used as a solute with the solvents water (W), ethyl alcohol (EA), ethylene glycol (EG), dimethyl sulphoxide (DMSO), acetone (Ac) and 1,4-dioxane (Dx), have been measured over the entire concentration range at 30 degrees C. The negative values of excess dielectric constant and less-than-unity values of the corrective Kirkwood correlation factor of these binary mixtures are used to analyse the formation of H-bond complexes and molar ratio of the stable adduct. In these systems, the unassociated mixture constituents, DMSO, Ac and Dx, act as structure-breakers for self-associated linear structures of NMF, whereas, both the self-associated mixture constituents (W, EA and EG mixtures with NMF) act as structure-breakers to each other during the complexations. It is found that the large variations in the strength of H-bond complexation and the effective number of parallel aligned dipoles in the mixtures are governed by the dielectric constant of the solvents.