Correlation analyses for bimolecular nucleophilic substitution reactions of chloroacetanilide herbicides and their structural analogs with environmentally relevant nucleophiles

Lippa, Katrice A.; Roberts, A. Lynn

doi:10.1897/04-450r.1

Cited by 8 publications

(12 citation statements)

References 34 publications

(98 reference statements)

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“…From the rate constants summarized in Table 1, it can be seen that the second-order rate constant of TCEP at 50 °C with thiophenolate is higher than the second-order rate constant with bisulfide. This is in good agreement with the difference in reactivity that has been reported for nucleophilic substitution reactions at a carbon center (Schwarzenbach et al, 2003; Lippa and Roberts, 2005; Wu et al, 2006). …”

Section: Resultssupporting

confidence: 92%

Reaction of tris(2-chloroethyl)phosphate with reduced sulfur species

2011

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Tris(2-chloroethyl)phosphates (TCEP) is a widely used flame retardant in the U.S. It has recently been identified as one of the most frequently detected contaminants in U.S. streams. This contaminant is of toxicological concern in sensitive coastal ecosystems such as estuaries and salt marshes. It is likely that reactions with reduced sulfur species such as polysulfides (Sn2−), bisulfide (HS−), and thiophenolate (PhS−) present in anoxic subregions of coastal water bodies could have a significant impact on rates of removal of such a contaminant. The kinetics of reaction of reduced sulfur species with tris(2-chloroethyl)phosphate have been determined in well-defined aqueous solutions under anoxic conditions. Reactions were monitored at varying concentrations of reduced sulfur species to obtain the second-order rate constants from the observed pseudo-first order rate constants. The determined second-order rate constant for the reaction of TCEP with polysulfide at 25°C is 5.0 (± 1.4) × 10−4 M−1 s−1, with thiophenolate at 50 °C is 34 (± 2) × 10−4 M−1 s−1 and with bisulfide at 50 °C is 0.9 × 10−4 M−1 s−1, respectively. In addition, the degradation products of hydrolysis and the reactions with polysulfides, thiophenolate, and bisulfide with TCEP were studied with GC-FID and LC-MS-MS and were quantified.

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Section: Resultssupporting

confidence: 92%

Reaction of tris(2-chloroethyl)phosphate with reduced sulfur species

2011

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“…Many reports point out the bimolecular substitution (S N 2) of the environmental nucleophiles (including the reduced sulfur) with the halogenated aliphatic species. − However, the nucleophilic aromatic substitution (S N Ar) seems not to be paid much attention. The reaction of ATZ with HS – and polysulfide belongs to the S N Ar reaction and would be an interesting subject to investigate .…”

Section: Resultsmentioning

confidence: 99%

Detoxification of Atrazine by Low Molecular Weight Thiols in Alfalfa (Medicago sativa)

Zhang

Feng

et al. 2017

Chem. Res. Toxicol.

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Low molecular weight (LMW) thiols in higher plants are a group of sulfur-rich nonprotein compounds and play primary and multiple roles in cellular redox homeostasis, enzyme activities, and xenobiotics detoxification. This study focused on identifying thiols-related protein genes from the legume alfalfa exposed to the herbicide atrazine (ATZ) residues in environment. Using high-throughput RNA-sequencing, a set of ATZ-responsive thiols-related protein genes highly up-regulated and differentially expressed in alfalfa was identified. Most of the differentially expressed genes (DEGs) were involved in regulation of biotic and abiotic stress responses. By analyzing the genes involved in thiols-mediated redox homeostasis, we found that many of them were thiols-synthetic enzymes such as γ-glutamylcysteine synthase (γECS), homoglutathione synthetase (hGSHS), and glutathione synthetase (GSHS). Using liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS), we further characterized a group of ATZ-thiols conjugates, which are the detoxified forms of ATZ in plants. Cysteine S-conjugate ATZ-HCl+Cys was the most important metabolite detected by MS. Several other ATZ-conjugates were also examined as ATZ-detoxified metabolites. Such results were validated by characterizing their analogs in rice. Our data showed that some conjugates under ATZ stress were detected in both plants, indicating that some detoxified mechanisms and pathways can be shared by the two plant species. Overall, these results indicate that LMW thiols play critical roles in detoxification of ATZ in the plants.

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“…Three different mechanisms were evaluated being the bimolecular nucleophilic substitution (S N 2) mechanism, with the most favorable one having activation free energies around 20 kcal/mol [13]. Under this approach, other anionic nucleophiles present in water bodies such as iodide and bromide ions have been experimentally considered for the S N 2 nucleophilic substitution reaction of chloroacetanilide [20].…”

Section: Introductionmentioning

confidence: 99%

“…2021, 22, x FOR PEER REVIEW 3 of 16 evaluated being the bimolecular nucleophilic substitution (SN2) mechanism, with the most favorable one having activation free energies around 20 kcal/mol [13]. Under this approach, other anionic nucleophiles present in water bodies such as iodide and bromide ions have been experimentally considered for the SN2 nucleophilic substitution reaction of chloroacetanilide [20]. In this study, the effect of the nucleophile nature in the SN2 mechanism, which has been reported as the most favorable mechanism for these reactions (Scheme 1), was theoretically evaluated in detail by employing the Density Functional Theory (DFT) with the long-range dispersion-corrected Head-Gordon hybrid functional B97XD .…”

Section: Introductionmentioning

confidence: 99%

Effect of the Nucleophile’s Nature on Chloroacetanilide Herbicides Cleavage Reaction Mechanism. A DFT Study

Cuesta

Torres

Rincón

et al. 2021

IJMS

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In this study, the degradation mechanism of chloroacetanilide herbicides in the presence of four different nucleophiles, namely: Br−, I−, HS−, and S2O3−2, was theoretically evaluated using the dispersion-corrected hybrid functional wB97XD and the DGDZVP as a basis set. The comparison of computed activation energies with experimental data shows an excellent correlation (R2 = 0.98 for alachlor and 0.97 for propachlor). The results suggest that the best nucleophiles are those where a sulfur atom performs the nucleophilic attack, whereas the other species are less reactive. Furthermore, it was observed that the different R groups of chloroacetanilide herbicides have a negligible effect on the activation energy of the process. Further insights into the mechanism show that geometrical changes and electronic rearrangements contribute 60% and 40% of the activation energy, respectively. A deeper analysis of the reaction coordinate was conducted, employing the evolution chemical potential, hardness, and electrophilicity index, as well as the electronic flux. The charge analysis shows that the electron density of chlorine increases as the nucleophilic attack occurs. Finally, NBO analysis indicates that the nucleophilic substitution in chloroacetanilides is an asynchronous process with a late transition state for all models except for the case of the iodide attack, which occurs through an early transition state in the reaction.

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Correlation analyses for bimolecular nucleophilic substitution reactions of chloroacetanilide herbicides and their structural analogs with environmentally relevant nucleophiles

Cited by 8 publications

References 34 publications

Reaction of tris(2-chloroethyl)phosphate with reduced sulfur species

Reaction of tris(2-chloroethyl)phosphate with reduced sulfur species

Detoxification of Atrazine by Low Molecular Weight Thiols in Alfalfa (Medicago sativa)

Effect of the Nucleophile’s Nature on Chloroacetanilide Herbicides Cleavage Reaction Mechanism. A DFT Study

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