Premium
Kinetics of chemical degradation of isoxaflutole: influence of the nature of aqueous buffers (alkanoic acid/sodium salt vs phosphate)
Author(s) -
Beltran Estelle,
Fenet Hélène,
Cooper JeanFrançois,
Coste CamilleMichel
Publication year - 2001
Publication title -
pest management science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.296
H-Index - 125
eISSN - 1526-4998
pISSN - 1526-498X
DOI - 10.1002/ps.300
Subject(s) - chemistry , substituent , aqueous solution , degradation (telecommunications) , phosphate , reaction rate constant , derivative (finance) , reagent , benzoic acid , salt (chemistry) , medicinal chemistry , ketone , sodium , kinetics , organic chemistry , nuclear chemistry , telecommunications , physics , quantum mechanics , computer science , financial economics , economics
A kinetic study of the chemical degradation of isoxaflutole (5‐cyclopropyl‐1,2‐oxazol‐4‐yl ααα‐trifluoro‐2‐mesyl‐ p ‐tolyl ketone) into its diketonitrile derivative (DKN), which is its active herbicide principle, in organic buffers at different pH values was carried out using a HPLC/UV detection method. The values of the pseudo‐first‐order rate constants K obs for the reaction were calculated and compared with those previously obtained in inorganic buffers. In both cases, K obs was found to be dependent on pH and temperature, but at pH 5.2 the degradation of isoxaflutole in CH 3 COOH/CH 3 COONa buffers was considerably faster than in KH 2 PO 4 /Na 2 HPO 4 buffers, indicating that the compound was sensitive to the nature of the reagents used to prepare buffered solutions. The influence of phosphate and acetate concentrations and the influence of the R‐substituent in RCOOH/RCOONa buffers were investigated. For the HA/A − buffers studied, the values of K obs were linearly dependent on HA and A − concentrations, which meant that the degradation of isoxaflutole was subject to general catalysis. The values of K obs were also found to be dependent on the number and the position of the CH 3 groups of the R‐substituent. The known degradation product of DKN (a benzoic acid derivative) was not detected throughout this study. © 2001 Society of Chemical Industry