Room-temperature and temperature-dependent QSRR modelling for predicting the nitrate radical reaction rate constants of organic chemicals using ensemble learning methods

Abstract

Experimental determinations of the rate constants of the reaction of NO₃ with a large number of organic chemicals are tedious, and time and resource intensive; and the development of computational methods has widely been advocated. In this study, we have developed room-temperature (298 K) and temperature-dependent quantitative structure–reactivity relationship (QSRR) models based on the ensemble learning approaches (decision tree forest (DTF) and decision treeboost (DTB)) for predicting the rate constant of the reaction of NO₃ radicals with diverse organic chemicals, under OECD guidelines. Predictive powers of the developed models were established in terms of statistical coefficients. In the test phase, the QSRR models yielded a correlation (r²) of >0.94 between experimental and predicted rate constants. The applicability domains of the constructed models were determined. An attempt has been made to provide the mechanistic interpretation of the selected features for QSRR development. The proposed QSRR models outperformed the previous reports, and the temperature-dependent models offered a much wider applicability domain. This is the first report presenting a temperature-dependent QSRR model for predicting the nitrate radical reaction rate constant at different temperatures. The proposed models can be useful tools in predicting the reactivities of chemicals towards NO₃ radicals in the atmosphere, hence, their persistence and exposure risk assessment.

Keywords:

• Nitrate radical
• organic chemicals
• kinetic rate constant
• temperature-dependent model
• chemical reactivities
• ensemble learning

Acknowledgments

The authors thank the Director, CSIR-Indian Institute of Toxicology Research, Lucknow and the CEO, ETRC, Lucknow for their keen interest in this work.