Kinetics and mechanism of cymoxanil degradation in buffer solutions
| Autor: | Steven Trabue, S Lynne Mattson, Sonya Lawler, R Scott Swain, Jeffrey J. Anderson, Patrizia Morrica, Paola Fidente, Serenella Seccia |
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| Přispěvatelé: | Morrica, Patrizia, Trabue, S, Anderson, Jj, Lawler, S, Seccia, Serenella, Fidente, Paola, Swain, R, Mattson, S. L. |
| Rok vydání: | 2004 |
| Předmět: |
Reaction mechanism
half-life Chemical Phenomena Stereochemistry Kinetics Oxalic acid Buffers Medicinal chemistry chemistry.chemical_compound Acetic acid Hydrolysis Acetamides hydrolysi Aqueous solution Cymoxanil pH Chemistry Physical Oxalic Acid Temperature General Chemistry Buffer solution Hydrogen-Ion Concentration Fungicides Industrial Solutions chemistry Thermodynamics General Agricultural and Biological Sciences Acetamide |
| Zdroj: | Journal of agricultural and food chemistry. 52(1) |
| ISSN: | 0021-8561 |
| Popis: | The kinetics and mechanism(s) of the hydrolytic degradation of a compound are needed to evaluate a compound's abiotic degradation in the environment. In this paper, the hydrolysis of cymoxanil [2-cyano-N-[(ethylamino)carbonyl]-2-(methoxyimino) acetamide] was investigated in dark sterile aqueous solutions under a variety of pH conditions (pH 2.8-9.2) and temperatures (15-50 degrees C). Hydrolysis of cymoxanil was described by first-order kinetics, which was dependent on pH and temperature. Cymoxanil degraded rapidly at pH 9 (half-life = 31 min) and relatively slowly at pH 2.8 (half-life = 722 days). The effect of temperature on the rate of cymoxanil degradation was characterized using the Arrhenius equation with an estimated energy of activation of 117.1 kJ mol(-)(1). An increase in temperature of 10 degrees C resulted in a decrease in half-life by a factor of approximately 5. Three competing degradation pathways are proposed for the hydrolysis of cymoxanil, with two of the pathways accounting for approximately 90% of cymoxanil degradation. These two pathways involved either initial cyclization to 1-ethyldihydro-6-imino-2,3,5(3H)-pyrimidinetrione-5-(O-methyloxime) (1, Figure 1) or direct cleavage of the C-1 amide bond to form cyano(methoxyimino) acetic acid (7). The third pathway of degradation involved initial cyclization to 3-ethyl-4-(methoxyimino)-2,5-dioxo-4-imidazolidinecarbonitrile (8), which rapidly degrades into 1-ethyl-5-(methoxyimino)-2,4-imidazoline-2,4-dione (9). All three pathways eventually lead to the formation of the polar metabolite oxalic acid. |
| Databáze: | OpenAIRE |
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