Thermochimica Acta, Vol.435, No.1, 49-56, 2005
Application of correlation-gas chromatography to evaluate the vaporization enthalpy of a component in an equilibrium mixture
The vaporization enthalpies and vapor pressures of acetoin, ethyl 3-hydroxybutyrate and ethyl 3-hydroxyhexanoate, found in a variety of foods and flavors, are evaluated at T = 298.15 K using correlation-gas chromatography; values of (48.7 +/- 0.4), (55.9 +/- 0.6) and (61.9 +/-0.6) kJ mol(-1), respectively, were obtained. These values are in good agreement with estimated values. Vapor pressures of the standards as a function of temperature were also used to calculate vapor pressures of the target compounds and all resulting data were fit to second order polynomials. These polynomials were then used to predict boiling temperatures of both standards and target substances. Agreement with experimental boiling temperatures was generally within 10 K suggesting that vapor pressures are accurate to within a factor of two. Acetoin exists as an equilibrium mixture of monomer and dimer. This report provides an example of the utility of using correlation-gas chromatography to obtain thermochemical data on an impure material. (C) 2005 Elsevier B.V. All rights reserved.