Kinetic and mechanistic studies on the interaction of thymidine with the hydroxopentaaquarhodium(III) ion |
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Authors: | Sudip K. Mukhopadhyay Alak K. Ghosh |
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Affiliation: | (1) Department of Chemistry, J.K. College, Purulia, West Bengal, India;(2) Department of Chemistry, National Institute of Technology, Durgapur, 713209, West Bengal, India |
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Abstract: | The interaction of thymidine, a nucleoside, with hydroxopentaaquarhodium(III), [Rh(H2O)5(OH)]2+ ion in aqueous medium is reported and the possible mode of binding is discussed. The kinetics of interaction between thymidine and [Rh(H2O)5OH]2+ has been studied spectrophotometrically as a function of [Rh(H2O)5OH2+], [thymidine], pH and temperature. The reaction has been monitored at 298 nm, the max of the substituted complex, and where the spectral difference between the reactant and product is a maximum. The reaction rate increases with [thymidine] and reaches a limiting value at a higher ligand concentration. From the experimental findings an associative interchange mechanism for the substitution process is suggested. The activation parameters ( H =47.8 ± 5.7 kJ mol–1, S =–173 ± 17 J K–1 mol–1) supports our proposition. The negative G0 (–13.8 kJ mol–1) for the first equilibrium step also supports the spontaneous formation of the outer sphere association complex. |
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