Development of a QSAR model for predicting aqueous reaction rate constants of organic chemicals with hydroxyl radicals

Abstract

Reaction with hydroxyl radicals (˙OH) is an important removal pathway for organic pollutants in the aquatic environment. The aqueous reaction rate constant (k_OH) is therefore an important parameter for fate assessment of aquatic pollutants. Since experimental determination fails to meet the requirement of being able to efficiently handle numerous organic chemicals at limited cost and within a relatively short period of time, in silico methods such as quantitative structure–activity relationship (QSAR) models are needed to predict k_OH. In this study, a QSAR model with a larger and wider applicability domain as compared with existing models was developed. Following the guidelines for the development and validation of QSAR models proposed by the Organization for Economic Co-operation and Development (OECD), the model shows satisfactory performance. The applicability domain of the model has been extended and contained chemicals that have rarely been covered in most previous studies. The chemicals covered in the current model contain functional groups including CC, –CC–, –C₆H₅, –OH, –CHO, –O–, CO, –CO(O)–, –COOH, –CN, N–, –NH₂, –NH–C(O)–, –NO₂, –NC–N, N–N, –NN–, –S–, –S–S–, –SH, –SO₃, –SO₄, –PO₄, and –X (F, Cl, Br, and I).