Study of Intermolecular Interactions in (Ethanol+ n- Heptanol + Acrylonitrile) Ternary Mixture Through Thermo-acoustic and Excess Parameters at Different Temperatures

Abstract

This research investigates the intermolecular interactions in the ternary liquid mixture of ethanol, n-heptanol, and acrylonitrile using thermo-acoustic parameters at 298.15, 303.15, and 308.15 K under atmospheric pressure. Ultrasonic velocity, viscosity, as well as density were experimentally measured over the entire composition range, and thermo-acoustic parameters like acoustic impedance, intermolecular free length, adiabatic compressibility, internal pressure, relaxation time, and free volume were evaluated using standard relations. The dip in ultrasonic density, velocity, along with acoustic impedance, together with the increase in intermolecular free length as well as adiabatic compressibility with rising ethanol concentration, indicates a gradual weakening of the self-associated hydrogen-bonded network of n-heptanol and reduced molecular packing. Rise in internal pressure and relaxation time proposes creation of heteromolecular associations through hydrogen bonding between the hydroxyl groups of ethanol and n-heptanol, along with dipole–dipole interactions involving the nitrile group of acrylonitrile. The observed variations demonstrate that the liquid structure is governed by the balance between the disruption of alcohol self-association and the formation of unlike molecular interactions. Increasing temperature weakens these interactions due to enhanced thermal agitation, resulting in reduced molecular association and structural ordering. The results confirm that thermo-acoustic parameters provide valuable insight in intermolecular interactions as well as structural behaviour of ethanol + n-heptanol + acrylonitrile ternary liquid system.