Kinetics and Mechanism of Iridium(III) Catalysed Oxidation of Some Polyhydroxy Alcohols by N-Bromoacetamide in Petrochloric Acid Medium

摘要

The kinetics of iridium(III) catalysed oxidation of ethylene glycol and dulcitol by N-bromoacetamide (NBA) in perchloric acid,in the presence of Hg(OAc)_2 as a scanenger for Br~- has been studied in the temperature range of 30-45 deg C.Similar kinetics was followed by both the polyhydroxy alcohls.The reactions exhibit a zero order dependence with respect to each polyhydroxy alchol and first order at low concentration range of [NBA] was observed to tend to zero order at its higher concentrations.The influence of Hg(OAc)_2 and ionic strength is insignificant.A negative fractional order in both [H~+] and [Cl~-] and a positive fractional order in Ir(III) are observed whereas successive addition of acetamide decreases the rate of oxidation.A suitable mechanism consistent wiht the observed kinetic datais proposed and activation parameters calculated.