Structural Properties of 1-Octanol/n-Octane Mixtures Studied by Brillouin Scattering

Abstract

Polarized Rayleigh-Brillouin spectra of 1-octanol/n-octane solutions at different mole fractions have been recorded in the temperature range of 5-70 °C by using a 90°scattering configuration. Hypersonic velocities and acoustic attenuations have been calculated by means of a fitting procedure with suitable Lorentzian functions. The relaxation of the liquid structure revealed by viscous and thermal energy losses has been interpreted and discussed in terms of a local H-bond network and conformational modifications. The thermal behavior of macroscopic parameters such as number density and shear viscosity has also been studied in the same temperature range in an effort to better interpret the observed relaxation processes and the distribution of their relaxation times.

Comparison of Hydrogen Bonding in 1-Octanol and 2-Octanol as Probed by Spectroscopic Techniques

“…Thus, it appears that when the hydrogen-bonding network is more extended the increase of the χ S with T is weaker. This is confirmed by the large temperature dependence of χ S in neat liquid octane (see the inset of Figure ) 1 Isoentropic compressibility of 1-oct and 2-oct calculated form Brillouin data.…”

“…Brillouin scattering spectra of the two alcohols were recorded between 5 and 70 °C, and the hypersonic velocities v h were evaluated by the measured Brillouin shift. , The isoentropic compressibility χ S was then calculated using the usual expression: where ρ is the mass density. In Figure , χ S is reported for the 1- and 2-isomers at different temperatures.…”

“…χ S is considerably higher for 2-oct in the entire range investigated. It is expected that this quantity decreases going from linear alkanes to the corresponding alkanols due to increasing H-bonding forces and that the effect should be more important for shorter alcohols. , Thus, for the 2-isomer H-bonds are less effective in decreasing χ S . The data also confirm that the χ S is a very sensitive probe of intermolecular interactions, since important differences can be detected even for two systems with very similar densities and with not dramatic changes of the overall self-association degree (see below).…”

“…Finally, hypersonic velocities are obtained via Brillouin scattering experiments, , and the hypersonic compressibilities are evaluated for the two pure samples at different temperatures. Since H-bonded networks show a marked tendency to preserve their configuration, the compressibility of microheterogeneous amphiphilic systems may provide information on the interchain potentials of the less rigid hydrophobic regions.…”

Hydrogen bonding in liquid and supercritical 1-octanol and 2-octanol assessed by near and midinfrared spectroscopy

“…Let us emphasize that neat and water-saturated octanol ͑1-octanol͒ are often used experimentally as membrane mimetics. In this respect, neat 1-octanol has been the subject of a large number of experimental and theoretical studies using near IR two dimensional ͑2D͒ technique, 13 x-ray diffraction, 14 Rayleigh-Brillouin, 15 Raman, and infrared 16,17 spectroscopies, and molecular dynamics simulations, 18,19 aimed at understanding its structure and dynamics under ambient conditions. Thus, it has been shown by molecular dynamics simulations that the structure of the pure liquid is characterized in terms of fluctuating regions of preferentially polar ͑hydroxyl groups͒ and nonpolar character ͑hydrocarbons͒, including inverted micelle aggregates.…”