Henryʹs law constants for a diverse set of organic chemicals: Experimental determination and comparison of estimation methods

The Henryʹs law constant (HLC) or air/water partition coefficient is a key property in the process of describing a chemicalʹs environmental fate. Compared to its significance, experimentally determined HLCs are known for a relatively small number of organic chemicals. We have measured HLCs for seven groups of compounds, i. e., aromatic hydrocarbons, aromatic nitro compounds, anilines, phenols, organochlorine pesticides, aliphatic alcohols, and aliphatic amines, using a thermodynamic method for the vast majority of compounds. These new data have been used to validate and compare existing estimation methods for HLCs, namely the vapor pressure / aqueous solubility ratio, the improved bond contribution method, and the group method. The improved bond contribution method, which can be applied to all compounds, turned out to produce the most reliable results. The vapor pressure / aqueous solubility approach gave slightly worse estimations whereas the group method was considerably worse. Shortcomings of the individual methods were discussed. E. g., the bond contribution method had a bad performance for the organochlorine pesticides.