Investigation of the Nucleophilic Attack of Dichlorvos by Reduced Sulfur Species Using ¹H NMR

The mechanism of the reaction of dichlorvos through hydrolysis reactions and through the reaction with polysulfide (S_n^2-) and thiophenolate (PhS^-) was investigated by proton nuclear magnetic resonance (¹H NMR). The study confirmed product identities of an organophosphorus insecticide reacting with reduced sulfur species using ¹H NMR in oxygen sensitive solutions. The experiments of dichlorvos with polysulfide led to the detection of a previously undetected product. The thiophenolate experiments were further advanced to investigate second-order rate kinetics using an internal standard. The experiments provide new evidence for a nucleophilic attack by the reduced sulfur species at the methoxy carbon of dichlorvos. In addition, the observation of in situ reaction dynamics illustrates the applicability of ¹H NMR spectroscopy toward kinetic investigations in environmental science.