Association of 1-hexanol in mixtures with n-hexane: Dielectric, near-infrared and DFT studies

Intermolecular Hydrogen Bonding in Associated Fluids: The Case of Isopentyl Alcohol Dissolved in Carbon Tetrachloride

Fourier-transform infrared (FTIR) spectra of isopentyl-alcohol dissolved in carbon tetrachloride (CCl4) were recorded as a function of concentration and temperature. Dilute isopentyl alcohol/CCl4 solutions were prepared in alcohol at concentrations of 1, 0.5, 0.3, 0.2, 0.1, 0.05, 0.02, 0.01, 0.005, 0.001 and 0.0005 M. Infrared absorption measurements were taken within a temperature range of 17-67 °C below the boiling point of the solutions. Decomposition of the spectral features corresponding to associated and unassociated species was performed to quantitatively follow the effect of temperature and concentration on intermolecular hydrogen bonding (HB) in isopentyl alcohol. The spectral feature in the 3600-3650 cm-1 frequency range attributed to the free OH stretching band was studied in detail to determine changes based on concentration and temperature variations. Computational methodologies were applied to evaluate the energetics and vibrational properties of the species involved in the structure in the gaseous state where no interactions are present. The results are discussed in view of relevant structural models to gain quantitative information concerning the effect of concentration and temperature on intermolecular hydrogen bonding.

Electrical Conductivity and Viscosity in Binary Organic Liquid Mixtures: Participation of Molecular Interactions and Nanodomains

The present work aims to shed light on recent literature reports suggesting that ionic species are implicated in the electrical conductivity of 1-octanol and its mixtures with hydrocarbons. Other workers have questioned this interpretation, and herein, based on new experimentation and with reference to various literature studies, we consider that molecular interactions are more likely to be responsible. To investigate this, we have studied mixtures of 1-octanol and either silicone oil (SO) or n-dodecane as nonpolar components, using dielectric (in particular electrical conductivity) and viscometric measurements. With reference to the literature, the self-association of alcohols is known to create microheterogeneity in the neat liquids and in mixtures with nonpolar, low dielectric constant liquids, and it has previously been considered to be responsible for the particular solvent properties of alcohols. The present results suggest that the electrical conductivity of alkane/alcohol systems may have similar origins, with percolating pathways formed from octanol-rich nanodomains comprising polar regions containing hydrogen-bonded hydroxyl groups and nonpolar regions dominated by alkyl chains. The percolation threshold found for dodecane/octanol mixtures, in which interactions between the component molecules are found from viscosity measurements to be repulsive, agrees well with results from experimental and theoretical studies of disordered arrangements of packed spheres, and moreover, it is consistent with other published alkane/alcohol results. On the other hand, the situation is more complex for SO/octanol mixtures, in which interactions between the two components are attractive, based on viscosity data, and in which the phase separation of SO occurs at high octanol concentrations. Overall, we have concluded that electrical conductivity in octanol (and potentially all liquid alcohols) and its mixtures with nonpolar molecules, such as alkanes, is consistent with the presence of conducting networks comprising octanol-rich nanodomains formed by self-association, and not as a result of ionic conduction.