Studies on the ketone-catalyzed decomposition of caroate in aqueous alkaline medium

✍ Scribed by S. Selvararani; B. Medona; M. S. Ramachandran

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 116 KB
• Volume: 37
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.20093

✦ Synopsis

Abstract

The kinetics of ketone‐catalyzed decomposition of caroate (peroxomonosulfate) was studied in aqueous alkaline medium at 25°C. The rate follows simple second‐order kinetics, first order in each [Ketone] and [PMS]. The rate constant values are independent of hydroxide ion concentrations over the range from 0.05 M to 0.15 M. The experimental results suggest that the nucleophilic addition of SO ion at the carbonyl carbon leads to the formation of oxirane intermediate in the rate‐determining step. Oxirane reacts rapidly with another SO to give the parent ketone, oxygen, and SO. The observed substituent effect on the activation energy E~A~ and Arrhenius (A) factor suggests that the electron‐donating substituents stabilize the activated state and make the entropy of activation more negative. This can be explained by the fact that the mechanism of oxirane formation shifts from concentric to nonconcentric process as we go from acetone to 3‐hexanone. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 483–488, 2005