Effect of isomeric butanols on the temperature corresponding to the adiabatic compressibility minimum of water

Abstract

The effect of isomeric butanols on the temperature corresponding to the adiabatic compressibility minimum of water (T β) was studied using a variablepath interferometer working at 3 MHz. The structural contribution to the shift inT β, [ΔT βstr]exp, was found to be positive and to increase with concentration to a maximum atX 2≃0.0193, 0.0100, and 0.0090 fort-butanol, sec-butanol, and isobutanol, respectively. The results have been explained on the basis of stabilization of water structure at low concentrations of alcohol. The quantity [ΔT βstr]exp forn-butanol is practically zero at low concentrations, while at high concentrations it is negative, indicating rupture of the hydrogen-bonded structure of water by this solute. At any given concentration,t-butanol > sec-butanol > isobutanol >n-butanol is the order of increasing structural contribution to the shift inT β. Theoretical values of the structural contribution to the shift inT β are in good agreement with the experimental data.