Acid- and Base-Mediated Hydrolysis of Dichloroacetamide Herbicide Safeners

• DOI: 10.1021/acs.est.1c05958
• Publication Date: 2021-12-18T04:07:52Z
• Authors: Monica E. McFadden; Eric V. Patterson; Keith P. Reber; Ian W. Gilbert; John D. Sivey; Gregory H. LeFevre; David M. Cwiertny
• Keywords: Amide; Base (topology)

Safeners are used extensively in commercial herbicide formulations. Although safeners regulated as inert ingredients, some of their transformation products have enhanced biological activity. Here, to fill gaps our understanding safener environmental fate, we determined rate constants and associated with the acid- base-mediated hydrolysis dichloroacetamide AD-67, benoxacor, dichlormid, furilazole. Second-order for (HCl) (NaOH) (2.8 × 10–3 0.46 0.3–500 M–1 h–1, respectively) were, many cases (5 8), greater than those reported chloroacetamide co-formulants. In particular, constant benoxacor was 2 orders magnitude that its active ingredient co-formulant, S-metolachlor. At circumneutral pH, only underwent appreciable (5.3 10–4 h–1), under high-pH conditions representative lime-soda softening, benoxacor's half-life 13 h─a timescale consistent partial during water treatment. Based on Orbitrap LC–MS/MS analysis product mixtures, propose structures major three distinct mechanistic pathways depend system pH compound structure. These include amide cleavage, acid-mediated oxazolidine ring opening. Collectively, this work will help identify systems which contributes dichloroacetamides, while also highlighting important differences reactivity dichloroacetamides