Vaporization Enthalpy and Vapor Pressure of Valproic Acid by Correlation Gas Chromatography

The vaporization enthalpy of valproic acid (2-propylpentanoic acid) is reported, and the vapor pressures of a series on aliphatic carboxylic acids are used to evaluate its vapor pressure as a function of temperature. The vaporization enthalpy was derived by correlation-gas chromatography. This resulted in a vaporization enthalpy, Delta H-vap(298.15 K) of (74.8 +/- 2.4) kJ.mol(-1). Vapor pressures from T/K = 298.15 to boiling temperature of valproic acid are also reported. A normal boiling temperature of T/K = 492.8 (lit., 494-5 K) and a vapor pressure of (2.2 +/- 0.3) Pa has been evaluated for valproic acid at T/K = 298.15. This compares favorably with an Environmental Protection Agency estimate of 6.1 Pa.