A theoretical study on the photodegradation mechanism of the endocrine disrupting chemical p-nonylphenol induced by OH in water.

Nonylphenol (NP) has attracted significant attention because of its widespread environmental presence, toxicity, and pseudo-estrogen properties. Photolysis is the main degradation pathway of many organic pollutants in water. In this study, the photodegradation mechanism of p-nonylphenol (p-NP) induced by OH in water was investigated using the density functional theory (DFT). Based on the calculations of charges using natural population analysis (NPA), the reaction of OH with NP included the carbon addition of a benzene ring and the hydrogen extraction of a phenolic hydroxyl group. The structures of all reactants, products, and intermediates were optimized at the B3LYP/6-31+G(d,p) level. Using vibrational frequency and intrinsic reaction coordinate analyses, the transition state and its reaction pathway were confirmed. Additionally, the solvent effect results showed the reaction preferably took place in water. Our results provide a theoretical basis for understanding the transformative process and assessing the potential risk of NP in the environment.