Molecular Interactions in [Hmim][NO₃] Ionic Liquid and 2-Alkanol Mixtures: Kirkwood–Buff Integrals and Structure Factor

Abstract

In this paper, the investigation on thermophysical properties, structure, and dominant interactions in the binary systems containing 1-hexyl-3-methylimidazolium nitrate ([Hmim][NO₃]) and 2-alkanol (2-propanol, 2-butanol, and 2-pentanol) were carried out through the Kirkwood–Buff (KB) integrals, structural factor, and excess molar volumes. Binary i and j parameters are positive and indicate that unlike molecules tend to form the strong interactions via forming hydrogen bonds and stay alongside while an increase in the carbon atom of 2-alkanols reduces the strength of bonds and tendency of the unlike molecules to be together. Also, the structure of mixtures was studied using the concentration–concentration structure factor, ${{S}_{{CC}}}(0)$. Results from the application of this parameter show that in all binary mixtures, heterocoordination is predominant, ordering occurs in solutions and fluctuations are less than random orientation. Moreover the chemical short-range order parameter α′, which is an important function to understand the complex formation and phase segregation in the liquid mixtures, was calculated and discussed for mentioned mixtures. For current binary mixtures, experimental data and theoretical investigations are novel and reported for the first time.