On the Mechanism of Ozonolysis of Glyphosate

Glyphosate is a commonly used herbicide. This compound is considered a probable human carcinogen; thus, an efficient and inexpensive method for promoting its facile decomposition into simpler and safer compounds is highly desirable. Ozone, a known disinfectant for aqueous solutions, is known to promote the degradation of glyphosate. The reaction between glyphosate and ozone under alkaline conditions was studied by a variety of spectroscopic techniques. We find that a glyphosate-ozone adduct is initially cleaved primarily into aminomethylphosphonic acid, AMPA, and glycine via an imine intermediate. Investigation of the pH dependence of the reaction, study of a quaternary amine derivative of this herbicide, and NMR analyses of ¹³C- and ¹⁵N-labeled glyphosate analogues support our proposed mechanism. Finally, AMPA and glycine undergo a mechanistically similar degradation as glyphosate and are converted to inorganic products.