On apomorphine detection by colour reactions

In this communication the reaction routs of the Grimbert/Leclrc and Helch tests for apomorphine have been established.In the first assay an acid-base reaction occurs first between a phenol group in apomorphine and the acetate anion from the sodium salt.The resulting phenoxide displaces a chloride ion from HgCl2, the reagent.The mixed mercury oxychloride is labile and splits off in a phenoxyl radical and HgCl.The same process is repeated with the other hydroxyl group.A biradical is formed in the apomorphine molecule which reacts with the intermediate carbon-carbon double bond.A 1,2-benzoquinone and Cl-Hg-Hg-Cl are formed.In the Helch test the dichromate anion reacts with hydrochloric acid from morphine hydrochloride.Protonation of dichromic acid yields chromic acid and chromium trioxide.The latter reacts with a phenolic group by acid catalysis yielding a mixed chromate.Protonation of this ester affords chromous acid and an ortho-quinone.