A linear solvation energy relationship to predict vapor pressure from molecular structure

Abstract

Vapor pressures (in Pa at 298 K) of organic liquids were found to correlate (R2 = 0.986) with empirical molecular parameters by the relationship: log Pvap = 7.86 - 3.54 V - 1.17 E - 1.52 (S + λ) - 3.64 (η × A × B) where V, E, S, A, and B are solute parameters developed by Abraham and coworkers representing, respectively, the characteristic volume, excess index of refraction, dipolarity/polarizability, and hydrogen bond donor and acceptor characteristics of the solute. The parameter λ provides for modulation of the S term for specific functional groups, such as those with strongly dipolar structures, while the parameter η takes into account differences in neat-liquid hydrogen bonding between classes of liquids. This linear free energy relationship (LSER), together with appropriate solute parameters taken from literature data or estimated from chemical structure, provides a convenient method for estimating the vapor pressure of pure organic liquids. This study also provides insight into the extent to which the LSER model may be extended to the prediction of properties of pure substances. ©2005 Sociedade Brasileira de Química.