Osmium(VIII) catalysed oxidation of 6-aminopenicillanic acid by diperiodatoargentate( III) in aqueous alkaline medium by stopped flow technique
| Main Authors: | S. D. Gunagi, S. T. Nandibewoor, S. A. Chimatadar |
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| Format: | Article |
| Bahasa: | eng |
| Terbitan: |
, 2011
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| Subjects: | |
| Online Access: |
https://zenodo.org/record/5787869 |
Daftar Isi:
- P.G. Department of Studies in Chemistry, Karnatak University, Dharwad-580 003, Karnataka. India E-mail : schimatadar@gmail.com Manuscript received 06 September 2010, revised 30 December 2010, accepted 30 December 2010 The kinetics of micro amounts (10-7 mol dm-3) of osmium(VIII) catalysed oxidation of 6-aminupenicillanic acid by diperiodatoargentate(lll) in alkaline medium at 25 °C and at a constant ionic strength of 0.04 mol dm-3 was studied spectrophotometrically. The oxidation products were confirmed by IR, LC-ESI-l\IS and NMR spectral studies as 2-formyl-5,5-dimethylthiazolidine-4-carboxylic acid and silver(l). The stoichiometry is I : l i.e. one mole of diperiodatoargentate(lll) requires one mole of 6-aminopenicillanic acid. The reaction is first order with respect to diperiodatoargentate(lll) and catalyst, osmium(vm) concentrations, whereas less than unit order in both 6-aminopenicillanic acid and alkali. The oxidation reaction in alkaline medium has been shown to proceed via a osmium(VIII)-6- aminopenicillanic acid complex, which further reacts with one molecule of monoperiodatoargentate(lll) in a rate determining step followed by other fast steps. The active species of catalyst and oxidant have been identified 111Jd a suitable mechanism is proposed. The reaction constants involved in the different steps of the mechanism were calculated. The catalytic constant (Kc ) was also calculated at 25 °C. The activation parameters with respect to slow step of the mechanism were computed and discussed. The thermodynamic quantities were also determined.