Theoretical studies on the OH-initiated photodegradation mechanism of dicofol

Dicofol (2,2,2-trichloro-1,1-bis(4-chlorophenyl)ethanol) is an extensively used organochlorine acaricide. It has been regarded as an important environment pollutant because of its potential adverse effects on humans and the environment. In this paper, the OH-initiated photodegradation mechanism of dicofol is investigated elaborately and comprehensively at the B3LYP/6-311++G** level by performing DFT calculations. The frontier electron densities and bond dissociation energies are calculated to predict the position vulnerable to be attacked by OH radicals. The profile of the potential energy surface was constructed, and the possible pathways involved in the reaction are discussed. The theoretical studies show that OH attacking the C7–C8 bond and the addition of OH to the C12 atom of dicofol are both energetically and kinetically favorable pathways. The most dominant product of the photodegradation process is (C6H4Cl)2CO, which is in good agreement with the experimental observation result. More interestingly, one important precursor for forming PCDD/Fs, C6H4ClOH (4-CP), is detected in the degradation reactions.