QSPR Prediction of Henry’s Law Constant: Improved Correlation with New Parameters

Abstract

Henry’s law constant (H) is the air-water partition coefficient, and as such is important in modelling the environmental distribution of chemicals. Several quantitative structure-property relationship (QSPR) studies have been made of Henry’s law constant; we recently (Dearden et al., 1997) developed such a QSPR for 294 diverse compounds from a consideration of the fundamental processes occurring during air-water partitioning, and using only calculated parameters:

$$\begin{array}{*{20}{c}} {\log H = - 0.294H{B_N} - 0.957H{B_I} - 1.86\Delta MR + 0.998\log P - 1.11MR} \\ { + 0.356B{I_{dw}}/100 + {{0.229}^4}X_p^v + 0.579} \\ {\begin{array}{*{20}{c}} {n = 294}&{{r^2}\left( {adj} \right) = 0.874}&{s = 0.769}&{F = 292.5} \end{array}} \end{array}$$

(1)

where: HB_N = total number of hydrogen (H) bonds that a molecule can form with water; HB_I = sum of indicator variables for H-bond donation and acceptance; ∆MR = excess molar refractivity; log P = calculated logarithm of octanol-water partition coefficient; MR = calculated molar refractivity; BI_dw = Bonchev index; and ${}^4X_p^v$ = 4th order valence-corrected path molecular connectivity.