Kinetic study on acid-base catalyzed hydrolysis of azimsulfuron, a sulfonylurea herbicide

✍ Scribed by M. Niyaz Khan; Baki B. Bakar; Fenny W. N. Yin

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 152 KB
• Volume: 31
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/(sici)1097-4601(1999)31:4<253::aid-kin2>3.0.co;2-x

✦ Synopsis

Pseudo-first-order rate constants (k obs ) for hydrolysis of a sulfonylurea herbicide, azimsulfuron, AZIM, {N-[[(4,6-dimethoxy-2-pyrimidinyl)

] 2 within the [NaOH] range of 0.1-2.0 M at different temperatures ranging from 40 to 55ЊC. The contribution of ␣ 3 [ Ϫ OH] 2 term is small compared with ␣ 2 [ Ϫ OH] term and this turns out to be zero at 60ЊC. Pseudo-first-order rate constants (k obs ) for hydrolysis of AZS within the [H ϩ ] range from 2.5 ϫ 10 Ϫ6 to 1.4 M follow the relationship:

where pK a ϭ 4.37 at 50ЊC. The value of ␤ 1 is nearly 25 times larger than that of ␣ 1 . The rate of alkaline hydrolysis of AZIM is weakly sensitive to ionic strength.