Mechanism study on OH-initiated atmospheric degradation of the organophosphorus pesticide chlorpyrifos

Zhou, Qin; Sun, Xiaoyan; Gao, Rui; Zhang, Qingzhu; Wang, Wenxing

doi:10.1016/j.theochem.2010.03.023

Cited by 20 publications

(11 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[1,2,9,[11][12][13][14][15][16][17] Previous experimental and theoretical studies on OPs containing AOCH 3 or AOCH 2 A reported that reactions of these OPs with O 2 /NO result in the formation of an alkoxy radical ([P(O)OCH(OÁ)A). [12,15,[18][19][20][21][22] These results are in agreement with a subsequent rearrangement of the alkoxy radical occurring through a five-member transition state with the formation of [P(O)OH and a molecular carbonyl radical. In a recent experimental study, [23] the rate constant for atmospheric reaction of OH radicals and a simulant OP containing the AOCH\ and AOCH 3 groups isopropyl methyl methylphosphonate (IMMP, (CH 3 ) 2 CHO-P(O)(CH 3 )OCH 3 ) was determined to be 6.72 Â 10 À11 cm 3 mol À1 s…”

Section: Introductionsupporting

confidence: 75%

Atmospheric degradation mechanisms of a simulant organophosphorus pesticide isopropyl methyl methylphosphonate: A theoretical consideration

Zeng

2012

Int J of Quantum Chemistry

View full text Add to dashboard Cite

[a] Calculations using density functional theory were performed to explore the mechanisms for atmospheric degradation of isopropyl methyl methylphosphonate (IMMP). The potential energy surface profiles for OH-initiated reaction of IMMP were constructed, and all possible degradation channels were considered. Rate constants were further calculated using transition state theory. It was established from these calculations that H-abstractions from alkyl groups have much lower energy barriers than substitutions of alkoxyl groups, and four possible H-abstraction channels are competitive.Investigations into the secondary reactions under the presence of O 2 /NO were also performed. It is shown that O 2 addition, reaction of peroxide radicals with NO to form RO radicals, and removal of ÁRO are the major degradation pathways for alkyl radicals. Four selected products, CH 3 OP(O)(CH 3 )OC(O)CH 3 , CH 3 OP(O)(O)CH 3 , (CH 3 ) 2 CHOP(O)(CH 3 )OH, and (CH 3 ) 2 CHOP(O) (CH 3 )OCH¼ ¼O, are predicted to be the major products in this study.

show abstract

Section: Introductionsupporting

confidence: 75%

Atmospheric degradation mechanisms of a simulant organophosphorus pesticide isopropyl methyl methylphosphonate: A theoretical consideration

Zeng

2012

Int J of Quantum Chemistry

View full text Add to dashboard Cite

show abstract

“…This may have been due to the continued volatilization, wind erosion, and drift of CPF and CPF-O 24 hours following application (Zhou et al 2010). In Figure 3, the community samples report significantly higher concentrations CPF-O (ng/m3) and %CPF-O than in the orchard perimeter samples on both PUF and OVS tubes.…”

Section: Discussionmentioning

confidence: 99%

Comparison of polyurethane foam and XAD-2 sampling matrices to measure airborne organophosphorus pesticides and their oxygen analogs in an agricultural community

et al. 2013

View full text Add to dashboard Cite

Side-by-side active air sampling for the organophosphorus (OP) pesticide, chlorpyrifos (CPF) and its oxygen analog, chlorpyrifos-oxon (CPF-O) was conducted with two recommended air sampling matrices: OSHA Versatile Sampling (OVS) tubes with XAD-2 resin, polyurethane foam (PUF) tubes, and passive PUF deposition disks. The study compared the proportion of artificially transformed CPF-O in the laboratory and in the field during a tree fruit application in Washington State. Lab results demonstrated that the NIOSH-recommended OVS tubes artificially transformed up to 32% of CPF to CPF-O during the sampling process, whereas PUF tubes had little to no artificial transformation (≤ 0.1%). In the field, the proportion of CPF-O in the sample was significantly higher on OVS tubes than on PUF tubes (p < 0.001), confirming that OVS tubes were converting a significant portion of CPF to CPF-O. In addition, PUF tubes reported measurable levels CPF-O in the field even when no artificial transformation was expected. We conclude that the PUF matrix is the superior sampling medium for OP oxygen analogs when compared to XAD-2 resin. Community-located PUF tube samples 24 hours post-application had considerably higher levels CPF-O (16–21 ng/m3) than near field samples during application (2–14 ng/m3), suggesting that the oxygen analog is volatile and formed during atmospheric transport. It is recommended that worker and community risk assessments begin to take into consideration the presence of the more toxic oxygen analogs when measuring for OP pesticide mixtures.

show abstract

“…Interestingly, it is not difficult to realize that Prod-A, contrary to Prod-B and Prod-C, resembles what has so far been thought of this unimolecular decomposition. 6,14,19 It is worth mentioning, however, that an extra reaction step is now necessary to account for the complete formation of DAP in both pathways B and C as it is the case for the formation of TCP in pathway A, similar to previous work. The gain is still remarkable in that one of the main carbon-containing products (TCP) is formed in a single step in both pathways B and C. The fractional occupation number weighted electron density (FOD) analysis (see the SI for details) shows that most electrons behave as in closed-shell systems, being correlated those of active sites and some neighboring groups mostly in the product complexes.…”

Section: Resultsmentioning

confidence: 52%

Revisiting the Tropospheric OH-Initiated Unimolecular Decomposition of Chlorpyrifos and Chlorpyrifos-Methyl: A Theoretical Perspective

et al. 2020

View full text Add to dashboard Cite

Based on density functional theory (DFT) electronic structure calculations with dispersion correction, we propose new reaction pathways in which no extra reaction step is necessary to account for the formation of 3,5,6trichloro-2-pyridynol (TCP) within the process of tropospheric OH-initiated unimolecular decomposition of chlorpyrifos (CLP) and chlorpyrifos-methyl (CLPM). Chlorpyrifos and its analogous compound are among the most used organophosphorus pesticides worldwide, and their unimolecular decomposition in the troposphere is a dominant process of removal in the gas phase. The reaction pathways that we put forward have turned out to be the most exergonic ones among the three possible routes for the attack of the hydroxyl radical to the thiophosphoryl (PS) bond of both CLP and CLPM. The results showed that the reaction is thermodynamically controlled with the formation of P-bonded adducts via a six-membered ring. The unimolecular decomposition of such reactive intermediates takes place with small energy barriers (less than 3 kcal mol −1 ) and is distinguished by hydrogen transfer to the nitrogen atom of the aromatic ring, resulting in the formation of 3,5,6trichloro-2-pyridinol (TCP) and dialkyl phosphate radical (DAP•) product complexes in a single step.

show abstract

Mechanism study on OH-initiated atmospheric degradation of the organophosphorus pesticide chlorpyrifos

Cited by 20 publications

References 30 publications

Atmospheric degradation mechanisms of a simulant organophosphorus pesticide isopropyl methyl methylphosphonate: A theoretical consideration

Atmospheric degradation mechanisms of a simulant organophosphorus pesticide isopropyl methyl methylphosphonate: A theoretical consideration

Comparison of polyurethane foam and XAD-2 sampling matrices to measure airborne organophosphorus pesticides and their oxygen analogs in an agricultural community

Revisiting the Tropospheric OH-Initiated Unimolecular Decomposition of Chlorpyrifos and Chlorpyrifos-Methyl: A Theoretical Perspective

Contact Info

Product

Resources

About