Development of a quantitative structure-activity relationship model for predicting quantum yield of hydroxyl radical...

Organic compounds are capable of generating hydroxyl radicals (˙OH) through their excited triplet states in natural water. It is of significance to reveal the underlying mechanism of the generation and obtain the generation quantum yield of ˙OH from organic compounds for better understanding of its involvement in indirect photochemical processes in the environment. In this study, the ˙OH quantum yields (Φ_˙OH) of 20 organic compounds were determined by photochemical experiments. The calculated Φ_˙OH values for the selected organic compounds vary from (1.2 ± 0.39) × 10^-5 to (7.2 ± 0.16) × 10^-4. A quantitative structure-activity relationship (QSAR) model for log Φ_˙OH was developed and the established model was proven to have a proper goodness of fit, robustness, and predictive ability. The QSAR model was successfully used to predict the Φ_˙OH value of organic pollutants. Mechanistic interpretation showed that the electron distribution and the electronegativity of organic compounds are the most important factors that determine the generation of ˙OH. The results are helpful for understanding the generation mechanism of ˙OH from organic compounds and also provide insights into the generation of ˙OH from dissolved organic matter in natural water.