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

Abstract

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°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.

Keywords:

• dielectric constant
• binary mixtures
• molecular interactions

Acknowledgements

The authors thank the University Grants Commission, New Delhi, for a project grant (F. no. 33–15/2007 (SR)) under which the work was carried out. The Department of Science and Technology, Government of India, New Delhi, is kindly acknowledged for providing experimental facilities through the project (SR/S2/CMP–09/2002). One of the authors S. Sankhla is grateful to the CSIR, New Delhi, for providing an RA fellowship.