Copper(II)-promoted aqueous decomposition of Aldicarb

Bank, Shelton; Tyrrell, R. J.

doi:10.1021/jo00224a058

Cited by 14 publications

(6 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, the rate of degradation is significantly faster than in Cu II -free solutions of the same composition (a significant difference is apparent when reactions are monitored for three months). These findings are consistent with earlier studies that attribute Cu II -facilitated degradation of oxamyl and related carbamates to metal ion catalysis of the E1cb reaction (9,33).…”

Section: Resultssupporting

confidence: 93%

“…No direct evidence for the role of metal ion-carbamate coordination was obtained in this study. We expect that any bonding between Fe II and Lewis base groups present on the carbamates would be weak and difficult to detect by spectroscopic methods (33). Indirect evidence, however, indicates that metal ion coordination is not an essential component of the reaction mechanism.…”

Section: Resultsmentioning

confidence: 97%

“…Oximes and oxime esters are well known for their ability to form coordination complexes with transition metals (41). In addition, metal ion coordination by oxime esters has often been considered an important factor in metal ion-catalyzed hydrolysis of these compounds (9,33,42).…”

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Reduction of the Carbamate Pesticides Oxamyl and Methomyl by Dissolved Fe^IIand Cu^I

Strathmann

Stone

2001

Environ. Sci. Technol.

View full text Add to dashboard Cite

The degradation of two oxime carbamate pesticides, oxamyl and methomyl, was investigated in anoxic solutions containing various metal ions and reducing agents. In reagent-free solutions, these carbamates degrade slowly via base-catalyzed elimination. Rates of carbamate degradation are accelerated by Fe(II), Cu(I), and Cu(II), but not by several other metal ions and reducing agents. In the presence of Fe(II), carbamates undergo a net two-electron reduction that is coupled to the sequential one-electron oxidation of two Fe(II) ions. The observed products are a substituted nitrile, methanethiol, and methylamine. A radical intermediate is inferred by polymerization of the radical scavenger acrylonitrile. Redox kinetics (i) vary with carbamate identity, (ii) exhibit first-order dependence on both Fe(II) and carbamate concentration, (iii) are relatively independent of pH, (iv) follow Arrhenius temperature dependence, and (v) are only indirectly influenced by the presence of O2. Coordinatively saturated Fe(II) complexes (Fe(II)EDTA2- and Fe(II)(CN)6(4-)) react with oxamyl at rates equal to and greater than hexaquo Fe(II), respectively, indicating that an inner-sphere Fe(II)-carbamate coordination complex is not required for electron transfer. Experimental results indicate that Cu(I) reduces the carbamates by the same mechanism as Fe(II) but at much higher rates. In contrast, Cu(II) acts as a catalyst for both elimination and reduction reactions.

show abstract

Section: Resultssupporting

confidence: 93%

Section: Resultsmentioning

confidence: 97%

See 1 more Smart Citation

Reduction of the Carbamate Pesticides Oxamyl and Methomyl by Dissolved Fe^IIand Cu^I

Strathmann

Stone

2001

Environ. Sci. Technol.

View full text Add to dashboard Cite

show abstract

“…Let us return now to the observation that Fe II species in which five or six coordination positions are occupied by the organic ligand exhibit less reactivity than the LFER would predict. Metal ion coordination is believed to be an important factor in the metal ion-catalyzed hydrolysis of oxime esters ( − ), and oxamyl possesses several Lewis base groups capable of coordinating Fe II ( , ). We can therefore postulate that outer-sphere Fe II -to-oxamyl electron transfer is significantly slower than electron transfer within an Fe II −oxamyl inner-sphere complex.…”

Section: Resultsmentioning

confidence: 99%

Reduction of Oxamyl and Related Pesticides by Fe^II: Influence of Organic Ligands and Natural Organic Matter

Strathmann

Stone

2002

Environ. Sci. Technol.

103

View full text Add to dashboard Cite

The reduction of oxamyl and related oxime carbamate pesticides (OCPs; methomyl and aldicarb) by FeII is an important pathway for the degradation of these compounds in soil and groundwater. A series of batch kinetic experiments was carried out to assess the effects that selected carboxylate and aminocarboxylate ligands have on these reactions. In the absence of FeII, no OCP reduction by the ligands is observed. In the presence of FeII, the rate of OCP reduction varies by several orders of magnitude and can be described by the expression k(red) = [FeII]sigma(i)k(i)alpha(i) where k(red) is the observed pseudo-first-order rate constant for OCP reduction, [FeII] is the total FeII concentration, alpha(i) is the fraction of each FeII species in solution, and k(i) is the second-order rate constant for OCP reduction by each FeII species. The reactivity of individual FeII species is dependent upon the standard one-electron reduction potential of the corresponding FeIII/FeII redox couple (E(H)o) and the availability of inner-sphere FeII coordination sites for bonding with Lewis base donor groups within the OCP structure. A linear free energy relationship is proposed. Kinetic measurements demonstrate that natural organic matter from the Great Dismal Swamp facilitates OCP reduction by FeII in the same manner as the individual organic ligands. Results from this study improve our understanding of the pathways and rates of pesticide degradation in reducing subsurface environments, especially those rich in organic matter.

show abstract

“…No significant increases in the hydrolysis rates for aldicarb sulfoxide and aldicarb sulfone were observed. Bank and Tyrrell [21] reported that cuprous and zinc ions catalyze the hydrolysis of aldicarb in distilled water solutions and, as mentioned earlier, Bromilow showed that ferrous ions also catalyze the hydrolysis of aldicarb…”

Section: Distilled Water Hydrolysis Repeatability Testsmentioning

confidence: 64%

Laboratory studies on mechanisms for the degradation of aldicarb, aldicarb sulfoxide and aldicarb sulfone

Lightfoot

Thorne

Jones

et al. 1987

Enviro Toxic and Chemistry

View full text Add to dashboard Cite

Experiments were performed in order to better define the degradation mechanisms and kinetics for aldicarb and its two metabolites, aldicarb sulfoxide and aldicarb sulfone. The mechanisms studied were oxidation in surface soil and saturated zone soil samples, degradation in saturated zone soil samples and distilled water hydrolysis. The studies showed that soil is an important mechanistic factor, probably because surface catalysis occurs. Temperature and pH are important factors in determining degradation rates. The experiments seem to indicate that microbial oxidation is an important degradation mechanism in the surface soil, but the breakdown of aldicarb residues to noncarbamates is largely the result of chemical hydrolysis. The reduction of aldicarb sulfoxide to aldicarb was observed in the presence of limestone but only after an incubation period of two to six months. No reduction of aldicarb sulfone to aldicarb sulfoxide was observed in these experiments. The complexity of degradation is such that laboratory studies can augment but not replace well‐designed experiments conducted under actual field conditions.

show abstract

Copper(II)-promoted aqueous decomposition of Aldicarb

Cited by 14 publications

References 0 publications

Reduction of the Carbamate Pesticides Oxamyl and Methomyl by Dissolved Fe^IIand Cu^I

Reduction of the Carbamate Pesticides Oxamyl and Methomyl by Dissolved Fe^IIand Cu^I

Reduction of Oxamyl and Related Pesticides by Fe^II: Influence of Organic Ligands and Natural Organic Matter

Laboratory studies on mechanisms for the degradation of aldicarb, aldicarb sulfoxide and aldicarb sulfone

Contact Info

Product

Resources

About

Copper(II)-promoted aqueous decomposition of Aldicarb

Cited by 14 publications

References 0 publications

Reduction of the Carbamate Pesticides Oxamyl and Methomyl by Dissolved FeIIand CuI

Reduction of the Carbamate Pesticides Oxamyl and Methomyl by Dissolved FeIIand CuI

Reduction of Oxamyl and Related Pesticides by FeII: Influence of Organic Ligands and Natural Organic Matter

Laboratory studies on mechanisms for the degradation of aldicarb, aldicarb sulfoxide and aldicarb sulfone

Contact Info

Product

Resources

About

Reduction of the Carbamate Pesticides Oxamyl and Methomyl by Dissolved Fe^IIand Cu^I

Reduction of the Carbamate Pesticides Oxamyl and Methomyl by Dissolved Fe^IIand Cu^I

Reduction of Oxamyl and Related Pesticides by Fe^II: Influence of Organic Ligands and Natural Organic Matter