On the Mechanism of the Murexide Reaction

The murexide test used for identification of uric acid is mentioned in many laboratory texts. It consists in the degradative oxidation of uric acid by means of nitric acid and then a combination to yield a two ring product, purpuric acid. This gives a purple colour on addition of ammonia. From the chemical structure of the final product, various compounds are known to intervene for its obtention. However, the course of their formation during the degradation-oxidation process has not been cleared up. Thus, a mechanistic approach has been provided, step by step, in order to clarify the reaction sequence until the end product. Other compounds also formed are treated too. The study is based on well known reactivities and experimental observations