Ramalingaiah and Jagadeesh, R. V. and Puttaswamy (2008) Os(VIII)-catalyzed mechanistic investigation of oxidation of some benzimidazoles by chloramine-T in alkaline medium: A kinetic approach. Catalysis Communications, 9 (6). 1443 - 1452. ISSN 1566-7367
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The kinetics of Os(VIII)-catalyzed oxidation of benzimidazole (BzlH) and 2-substituted benzimidazoles viz., 2-methylbenzimidazole (MeBzlH), 2-hydroxybenzimidazole (2-HyBzlH), 2-aminobenzimidazole (2-AmBzlH) and 2-phenylbenzimidazole (2-PhBzlH) by sodium-N chloro-p-toluenesulfonamide (chloramine-T; CAT) in presence of NaOH has been investigated at 303K. Under comparable experimental conditions, the oxidation reactions follow identical kinetics for all the five benzimidazoles with first order dependence each on CAT0 and substrate0 and fractional order dependence each on OH− and Os(VIII). The reactions were studied at different temperatures and the composite activation parameters have been computed. The calculated isokinetic temperature (β) of 380K obtained from enthalpy-entropy relationships and Exner correlations was much higher than the experimental temperature of 303K, indicating that the rate is under enthalpy control. Relative reactivity of oxidation of these follow the order: 2-MeBzlH>2-HyBzlH>2-AmBzlH>BzlH>IzlH>2-PhBzlH. This trend may be attributed to inductive effects. Further, the kinetics of Os(VIII)-catalyzed oxidation of these benzimidazoles have been compared with those of their uncatalyzed reactions (in the absence of catalyst) and found that the catalyzed reactions are 10–15 fold faster than the uncatalyzed reactions. The observed results have been explained by a plausible mechanism and the related rate law has been deduced.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | Benzimidazoles, Os(VIII)-catalysis, Oxidation-kinetics, Chloramine-T |
| Subjects: | C Chemical Science > Chemistry |
| Divisions: | PG Centre Mandya > Chemistry |
| Depositing User: | Manjula P Library Assistant |
| Date Deposited: | 23 Aug 2019 11:05 |
| Last Modified: | 23 Aug 2019 11:05 |
| URI: | http://eprints.uni-mysore.ac.in/id/eprint/6984 |
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