Nucleophilic Degradation of Fenitrothion Insecticide and Performance of Nucleophiles: A Computational Study

Abstract

Ab initio and density functional theory (DFT) calculations have been performed to understand the destruction chemistry of an important organophosphorus insecticide O,O-dimethyl O-(3-methyl-4-nitrophenyl) phosphorothioate, fenitrothion (FN), toward nucleophilic attack. Breaking of the P-OAr linkages through nucleophilic attack is considered to be the major degradation pathway for FN. One simple nucleophile, hydroxide (OH(-)), and two different α-nucleophiles, hydroperoxide (OOH(-)) and hydroxylamine anion (NH(2)O(-)), have been considered for this study. Nucleophilic attack at the two different centers, S(N)2@P and S(N)2@C, has been monitored, and the computed reaction energetics confirms that the S(N)2@P reactions are favorable over the S(N)2@C reactions for all the nucleophiles. All electronic structure calculations for the reaction are performed at DFT-B3LYP/6-31+G(d) level of theory followed by a refinement of energy at ab initio MP2/6-311++G(2d,2p) level. The effect of aqueous polarization on both the S(N)2 reactions is taken into account employing the conductor-like screening model (COSMO) as well as polarization continuum model (PCM) at B3LYP/6-31+G(d) level of theory. Relative performance of the two α-nucleophiles, OOH(-) and NH(2)O(-), at the P center has further been clarified using natural bond orbital (NBO), conceptual DFT, and atoms in molecules (AIM) approaches. The strength of the intermolecular hydrogen bonding in the transition states and topological properties of the electron density distribution for -X-H···S (X = O, N) intermolecular hydrogen bonds are the subject of NBO and AIM analysis, respectively. Our calculated reaction energetics and electronic properties suggest that the relative order of nucleophilicity for the nucleophiles is OOH(-) > NH(2)O(-) > OH(-) for the S(N)2@P, whereas for the S(N)2@C the order, which gets little altered, is NH(2)O(-) > OOH(-) > OH(-).

Catalytic hydrolysis of phosphodiesters by nucleophilic ions in gemini micellar media

“…Many research groups have reported the reactivity of α‐nucleophiles toward the cleavage of carboxylate and phosphate esters in micellar media. Furthermore, the computational calculations show nucleophilic reactivity for the substrate hydrolysis . Thus, the highly efficient catalytic activity may be induced by the unshared lone pair of electron on the adjacent center of BDMO and AHA.…”

“…Furthermore, the computational calculations show nucleophilic reactivity for the substrate hydrolysis. [48] Thus, the highly efficient catalytic activity may be induced by the unshared lone pair of electron on the adjacent center of BDMO and AHA. It has also been observed that the nucleophilic reactivity of α-nucleophiles is much higher than that predicted by the Bronsted relationship between nucleophilicity and basicity.…”

Decontamination of methyl parathion in activated nucleophilic systems based on carbamide peroxisolvate

“…However, the formation of peroxoborates in the investigated range of pH 9-10, which is described by equations (9) and (10), is almost an undeniable fact. This approach is widely used by researchers to interpret kinetic regularities and the mechanism of oxidation in the system Н 2 О 2 /В(ОН) 3 near electrophilic centers [17,18].…”

“…In addition, the reagents used in industrial technologies (alkalis, alkali metal alcohols, and amines) do not differ in their high reactivity to phosphoric and phosphonic esters [6]. The rate of decomposing MP and its analogues can be increased by the use of α-nucleophiles [8,9], the typical representative of which is the peroxide anion НОО - [10] and its derivatives -peroxoaniones [11].…”

Decomposition of O,S-dimethyl methylphosphonothiolate by ammonia on magnesium oxide: a theoretical study of catalytic detoxification of a chemical warfare agent

“…[4][5][6] In this regard, the compound O,S-dimethyl methylphosphonothiolate (DMPT) is an analogue of the chemical warfare agent, VX, due to its P-O and P-S linkages that have similar hydrolytic labilities. A number of theoretical investigations were performed for the thermal unimolecular decomposition, 18 hydrolysis, 19 and a-nucleophilic destruction 20 of such deadly agents. A number of theoretical investigations were performed for the thermal unimolecular decomposition, 18 hydrolysis, 19 and a-nucleophilic destruction 20 of such deadly agents.…”