Estimating enthalpy of vaporization from vapor pressure using Trouton's rule

The enthalpy of vaporization of liquids and subcooled liquids at 298 K (Delta H-VAP(o)) is an important parameter in environmental fate assessments that consider spatial and temporal variability in environmental conditions. It has been shown that Delta H-VAP(o) for non-hydrogen-bonding substances can be estimated from vapor pressure at 298 K (P-L(o)) using an empirically derived linear relationship. Here, we demonstrate that the relationship between Delta H-VAP(o) and P-L(o) is consistent with Trouton's rule and the Clausius-Clapeyron equation under the assumption that Delta H-VAP(o) is linearly dependent on temperature between 298 K and the boiling point temperature. Our interpretation based on Trouton's rule substantiates the empirical relationship between Delta H-VAP(o) and P-L(o) for non-hydrogen-bonding chemicals with subcooled liquid vapor pressures ranging over 15 orders of magnitude. We apply the relationship between Delta H-VAP(o) and P-L(o) to evaluate data reported in literature reviews for several important classes of semivolatile environmental contaminants, including polycyclic aromatic hydrocarbons, chlorobenzenes, polychlorinated biphenyls and polychlorinated dibenzo-dioxins and -furans and illustrate the temperature dependence of results from a multimedia model presented as a partitioning map. The uncertainty associated with estimating Delta H-VAP(o) from P-L(o) using this relationship is acceptable for most environmental fate modeling of non-hydrogen-bonding semivolatile organic chemicals.