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Alcoholysis and chemical hydrolysis of bensulfuron‐methyl
Author(s) -
SABADIE J.
Publication year - 1996
Publication title -
weed research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.693
H-Index - 74
eISSN - 1365-3180
pISSN - 0043-1737
DOI - 10.1111/j.1365-3180.1996.tb01673.x
Subject(s) - chemistry , hydrolysis , methanol , reaction rate constant , substituent , hydrolysis constant , yield (engineering) , urea , medicinal chemistry , organic chemistry , kinetics , physics , materials science , quantum mechanics , metallurgy
Summary Alcoholysis (methanol or ethanol) and hydrolysis (pH ≤ 8) of the herbicide bensulfuron‐methyl at 30 or 50^C involve only the breakdown of the urea part of the molecule. A high yield of the pyrimidinamine is always obtained, along with the corresponding carbamate (alcoholysis) or benzylsulfonamide (hydrolysis). The latter compound was easily cyclized (pH ≥ 6). In alkaline solution, the carbomethoxy substituent of the aromatic ring was preferentially hydrolysed. In all cases, the alcoholysis and hydrolysis rates could be described well with first‐order kinetics. Alcoholysis rate constants of bensulfuron‐methyl and bensulfuron ranged from 0.08 to 0.15 d −1 at 30^C. Hydrolysis rate constants of bensulfuron‐methyl, bensulfuron and benzylsulfonamide varied strongly with pH. The hydrolysis rate constant of bensulfuron‐methyl was minimal around pH 8. The hydrolysis rate constant of bensulfuron decreased with increasing pH, whereas that of benzylsulfonamide increased with increasing pH.