On the interaction of apomorphine with ammonium tellurate in acidic medium

Apomorphine is a very interesting compound, both from the chemical point of view and from the biological-medical side. Apomorphine derives from acid catalysed rearrangement of morphine. However, the reaction mechanism has not been understood even at the present, notwithstanding that a correct sequence was advanced recently, including accepted thermodynamic rules and avoiding forbidden steps by thermodynamics found in other proposals.
Apomorphine is a bioactive compound used to improve hypomobilia due to Parkinson’s disease. In the present communication the chemistry of Brociner’s test for apomorphine is provided, as well as the reaction mechanism. The test is based on the interaction of apomorphine with ammonium tellurate in sulphuric acid. The reactive species is protonated telluric acid generated in situ. An SN2 reaction with a phenol group in apomorphine gives a mixed tellurate, whose interaction with a hydrion produces a concerted reaction mechanism, involving a vicinal phenol group as well as a C=C double bond. Tellurious acid is eliminated and an ortho-benzoquinone is formed.