Kinetics of oxidation of l-histidine by tetrachloroaurate(III) ion in perchloric acid solution

The redox reaction is first order in both AuCl4- and histidine. An inner-sphere mechanism is suggested. The rate determining steps in the mechanism are shown. It is shown that the intermediate C1 decomposes at a rate about 103 faster than the rate of decomposition of C. It is also shown that the rate of formation of these intermediates (outer-sphere mechanism) cannot be rate determining.