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Kinetic study on acid‐base catalyzed hydrolysis of azimsulfuron, a sulfonylurea herbicide
Author(s) -
Khan M. Niyaz,
Bakar Baki B.,
Yin Fenny W. N.
Publication year - 1999
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/(sici)1097-4601(1999)31:4<253::aid-kin2>3.0.co;2-x
Subject(s) - chemistry , sulfonylurea , hydrolysis , reaction rate constant , medicinal chemistry , catalysis , kinetic energy , kinetics , organic chemistry , medicine , physics , quantum mechanics , insulin , endocrinology
Pseudo‐first‐order rate constants ( k obs ) for hydrolysis of a sulfonylurea herbicide, azimsulfuron, AZIM®, { N ‐[[(4,6‐dimethoxy‐2‐pyrimidinyl)amino]carbony]‐1‐methyl‐4‐(2‐methyl‐2H‐tetrazol‐5‐yl)‐1H‐pyrazole‐5‐sulfonamide} (AZS) follow an empirical relationship: k obs =α 1 + α 2 [ − OH] + α 3 [ − OH] 2 within the [NaOH] range of 0.1–2.0 M at different temperatures ranging from 40 to 55°C. The contribution of α 3 [ − OH] 2 term is small compared with α 2 [ − OH] term and this turns out to be zero at 60°C. Pseudo‐first‐order rate constants ( k obs ) for hydrolysis of AZS within the [H + ] range from 2.5 × 10 −6 to 1.4 M follow the relationship: k obs = (α 1 K a + B 1 [H + ] + B 2 [H + ] 2 )/([H + ] + K a ) where p K a = 4.37 at 50°C. The value of B 1 is nearly 25 times larger than that of α 1 . The rate of alkaline hydrolysis of AZIM is weakly sensitive to ionic strength. © 1999 John Wiley & Sons, Inc., Int J Chem Kinet 31: 253–260, 1999