Kinetics and mechanism of hydrogen peroxide oxidation of chromone-3-carboxaldehydes in aqueous acid and micellar media

✍ Scribed by M. Matha; L. B. T. Sundari; K. C. Rajanna; P. K. Saiprakash

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 615 KB
• Volume: 28
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/(sici)1097-4601(1996)28:9<637::aid-kin1>3.0.co;2-w

✦ Synopsis

Oxidation of chromone-3-carboxaldehyde (CCA) and substituted analogues by H,O, has been carried out in aqueous acid (HCI and H,SO, 1 and micellar media. Reaction kinetics indicated order in ICCAl as well as [H,O,I to be unity while it is a fraction ( I > n > 0) in [acid]. Reaction rates were found to be faster in the solvents of low-dielectric constant I D ) Added salt (KCI or ( N H , ),SO,) increased the rate of oxidation marginally On the basis of observed linearity of Amis plot and marginal positive salt effect, protonated CCA (en01 form of CCA, a cation) and H,O, [neutral molecule] were considered as reactive species in the rate limiting step Reaction rates were found to be enhanced significantly in anionic and nonionic micellar isodium dodecylsulfate (SDSI and Triton X-100 (Tx], respectively) media However, cationic rnicelles (cetyl trimethyl ammonium bromide (CTAB) I indicated marginal retardation effect Effect of anionic and cationic micelles has been interpreted in terms of electrostatic interactions, while that of nonionic micelles in terms OF hydrophobic interactions Structure-reactivity correlations have been interpreted by Hammett's equation Negative "p" (reaction constant] values indicated cationic transition state. 0