Development of a model for predicting hydroxyl radical reaction rate constants of organic chemicals at different temperatures

The reaction rate constants of hydroxyl radicals with organic chemicals (K-OH) are of great importance for assessing the persistence and fate of organic pollutants in the atmosphere. However, experimental determination of K-OH seems fairly unrealistic, due to the soaring number of the emerging chemicals additional to the large number of existing chemicals. Quantitative structure-activity relationship (QSAR) models are excellent choices for evaluating and predicting K-OH values. In this study, a QSAR model that can predict K-OH at different temperatures was developed by employing quantum chemical descriptors and DRAGON descriptors. The adjusted determination coefficient R-adj(2) of the model is 0.873, and the external validation coefficient (Q(ext)(2) is 0.835, implying that the model has satisfactory robustness and good predictability. Additionally, a QSAR model was also built for koH prediction at room-temperature (298 K). The development of the two models followed the guidelines for development and validation of QSAR models proposed by the Organization for Economic Co-operation and Development (OECD). The applicability domains of the current models were extended to several classes of compounds including long-chain alkenes (C-8-C-13), organophosphates, dimethylnaphthalenes, organic selenium and organic mercury compounds that have not been covered in the previous studies. (C) 2013 Elsevier Ltd. All rights reserved.