Kinetics and mechanism of N-chlorosuccinimide (NCS) oxidation of glycine in aqueous alkaline medium using Rh(III) as negative catalyst have been studied at 350C. The observed kinetic data suggest that order with respect to [NCS] is unity throughout its ten-fold variation. Making basis to pseudo-first-order rate constant (k1) values for varying concentration of glycine and OH� ions, it is concluded that the first -order kinetics observed at low concentration of each reactant changes to zero-order at its higher concentrations. The significant feature of the reaction under investigation is that there is inverse proportionality between pseudo-first-order rate constant (k1) and [Rh(III)]. Inverse fractional order in [NHS] and nil effect in [Cl�] were observed throughout their variations. The reaction rates remain unaffected by the change in ionic strength (m) and dielectric constant (D) of the medium. The reaction has been studied at four different temperatures and with the help of observed k1 values, various activation parameters including the entropy of activation (?S#) were calculated. Spectral studies for the verification of the formation of complex species during the course of reaction have been made by the help of Varian Cary 300 Bio UV-Vis spectrophotometer. Suitable mechanism, consistent with the observed kinetic data together with reactive species of NCS, Rh(III) and glycine in alkaline medium and spectrophotometric evidence for the formation of complex species, has been proposed for oxidation of glycine by NCS in presence of  Rh(III) as negative catalyst.

Role of Rh(III) as negative catalyst in N-chlorosuccinimide oxidation of glycine in alkaline medium: A kinetic and mechanistic study

239th National Meeting (2010)

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