Comparative kinetic studies on the alkaline hydrolysis of halogen substituted isocoumarins

Authors : H Badaruddin AHMAD, M Aslam MALANA, Muhammad YOUSAF

Pages : 381-386

Doi:10.3906/sag-1202-53

View : 18 | Download : 8

Publication Date : 0000-00-00

Article Type : Research Paper

Abstract :Kinetics of the hydrolysis of 3-insert ignore into journalissuearticles values(2`-chloro-6`-fluorobenzyl); isocoumarin insert ignore into journalissuearticles values(1);, 3-insert ignore into journalissuearticles values(4`-fluorophenyl);isocoumarin insert ignore into journalissuearticles values(3);, 3-insert ignore into journalissuearticles values(2`- fluorophenyl);isocoumarin insert ignore into journalissuearticles values(5);, 3-insert ignore into journalissuearticles values(2`-chlorophenyl);isocoumarin insert ignore into journalissuearticles values(7);, and 3-insert ignore into journalissuearticles values(4`-chlorophenyl);isocoumarin insert ignore into journalissuearticles values(9); were studied spectrophotometrically in the presence of aqueous solution of potassium hydroxide. The rates of hydrolyses for these isocoumarins were compared. The data for isocoumarin insert ignore into journalissuearticles values(1); were further investigated to probe the reaction mechanism. The dependence of pseudo-first order rate constant kobs on hydroxide ion concentration is fitted by the expression kobs = ko + k1[OH] + k2 [OH]2, showing the formation of monoanionic and dianionic tetrahedral intermediates during the course of reaction. The magnitude of ko shows significant participation of solvent in the reaction mechanism.
Keywords : Hydrolysis, isocoumarin, kinetics