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Oxidation of Piperazines by Bromamine-B in Acidic Buffer Medium: A Kinetic and Mechanistic Study.

Chandrashekar, BM Venkatesha, S Ananda and Netkal M Made Gowda

The kinetics of oxidation of piperazine and its derivatives, 1-methylpiperazine and 1-ethylpiperazine, by N-sodio-N-bromobenzenesulfonamide or bromamine-B (BAB) in pH 4.0 buffer has been investigated at 303K. The reaction rate shows a first-order each on [BAB]0, and [Piperazine]0, and an inverse fractional-order dependence on[H+]. Additions of reaction product, benzenesulfonamide, or bromide ions and the variation of ionic strength of the medium have no influence on the reaction rate. The reaction has been studied at different temperatures and activation parameters have been calculated. A general mechanism consistent with the preceding kinetic data has been proposed and the rate law derived. The protonation constants of piperazine and its substituted derivatives have been evaluated. The Hammett correlation of substituent effect shows a linear free energy relationship with  = -0.75 indicating that electron donating centers enhance the rate of reaction. An isokinetic temperature of  = 393 K indicates that enthalpy factors control the reaction rate.