A Volumetric Study of Several Neat Alcohols as a Function of Temperature

Abstract

The temperature-dependent molar volumes of 14 neat alcohols, including the homologous set of straight-chain primary alcohols, selected secondary alcohols, ethylene glycol, and selected alcohols with deuterated hydroxyl groups were measured in anticipation of uncovering systematic properties applicable to other neat liquids. For example, the addition of a single methylene group sequentially from ethanol to n-heptanol increases the molar volume by the nearly constant value of 16.385 ± 0.019 cm³·mol⁻¹ at 0 °C. This linear behavior is exhibited at all temperatures studied. This constitutive property of molar volumes was reported previously for the partial molar volumes of aqueous alcohols, poly[vinyl alcohol], and organo-metallic complexes. Moreover, a method is proposed to partition the molar volumes into portions dependent upon intermolecular interactions, both attractive and repulsive (herein referred to as V_int, the apparent intrinsic volume), as well as a portion reflecting the tendency for molecules to separate due to thermal kinetic energy (herein referred to as V_exp, the expansive volume).