Organophosphate
(OP) pesticides are responsible for numerous human
deaths every year. Nucleophilic substitution is an important method
to mitigate the toxicity of obsolete stocks of OPs. Herein, the degradation
of O,O-diethyl-2,4-dinitrophenyl
phosphate (DEDNPP) and pesticide diethyl-4-nitrophenyl phosphate (Paraoxon)
promoted by 1,2,4-triazole (TAZ) was investigated by means of kinetic
studies, nuclear magnetic resonance (NMR) analyses, and theoretical
calculations. Results showed fast degradation of OPs is promoted by
the anionic form of the nucleophile (TAZ(−)) in pH > 8.5
(optimal
at pH = 11). Rate enhancements of 106 and 105-fold in relation to neutral hydrolysis of DEDNPP and Paraoxon were
observed, respectively, consistent with alpha-nucleophiles reactivity.
TAZ(−) regioselectively promotes the degradation of DEDNPP
via P–O bond break, forming a quickly hydrolyzable phosphorylated
intermediate, regenerating the nucleophile. Calculations using M06-2X/6-311++G(d,p)
level of theory revealed that the equivalent nitrogen atoms of TAZ(−)
are the main nucleophilic center of the molecule. This study expands
the knowledge on the reactivity of iminic compounds as detoxificant
agents of OPs, indicating the efficiency and selectivity of TAZ(−)
in aqueous medium, encouraging the design of novel TAZ-based catalysts.
The harmful impact caused by pesticides on human health and the environment necessitates the developmento fe fficient degradation processes and control of prohibited stocks of such substances. Organophosphates (OPs) are among the most used agrochemicals in the world and their degradation can proceed through several possible pathways. Investigatingt he reactivity of OPs with nucleophilic speciesa llows one to propose new and efficientc atalyst scaffolds for use in detoxification. In light of the remarkable catalytic activity of imidazole (IMZ) at promoting dephosphorylation processes of OPs, the reactivity of 4(5)-hy-droxymethylimidazole( HMZ) with diethyl-2,4-dinitrophenylphosphate (DEDNPP) and Paraoxon are evaluatedb y combining experimental andtheoretical approaches.I tisobservedt hat HMZ is an efficient and regiospecific catalyst with reactivity modulated by competing tautomers. To propose an optimal IMZ-based catalyst, quantumc hemical calculations were performed for monosubstituted 4(5)IMZ derivativest hat might cleave DEDNPP.B oth inductivee ffects and hydrogen bonding by the substituents are shown to influence barriers and mechanisms.[a] Prof.Supporting information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.
The breakdown of O,O-diethyl-2,4-dinitrophenyl phosphate (DEDNPP) in formamide (FMD) solutions is assessed using kinetic studies and 31P nuclear magnetic resonance (NMR). Regiospecific nucleophilic amidolysis via P–O bond cleavage is observed,...
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