Dielectric relaxation and hydrogen bonding in organic binary mixtures: experimental and theoretical analysis

The dielectric behaviour of n-hexanol + N,N-dimethylformamide binary mixtures was investigated at 313.15 K over the frequency range 20 Hz–2 MHz using dielectric spectroscopy. The complex permittivity, electric modulus, AC conductivity, and impedance formalisms were analysed to understand relaxation dynamics and charge transport mechanisms. The results reveal pronounced dipolar relaxation and significant electrode polarisation effects, indicating strong intermolecular interactions. Linear and mutual correlation factors, excess Helmholtz free energy, and excess molar polarisation were evaluated to probe molecular association. The analysis confirms dominant hydrogen bonding and dipole–dipole interactions between unlike molecules, along with contributions from long-range dipolar correlations and short-range self-association. The static dielectric constant was theoretically estimated using Luzar’s hydrogen bonding model to determine binding energy and enthalpy of association. Additionally, various dielectric mixing rules were assessed through average percentage deviation analysis. The study provides detailed insight into molecular organisation and interaction mechanisms in alcohol–amide solvent systems.