The chemistry of the Wellcome test for morphine

The use of chlorinated lime for morphine identification has several advantages. The reaction is fast and simple, and the reagent is inexpensive. Besides, the developed red colour comes from the organic compound, not from a reduced inorganic reagent. The last case only indicates oxido-reduction reaction, but it is alien to the final structure of the organic compound under test. In the Wellcome assay the red colour is typical of an o-quinone, the inorganic compounds being colourless. Since the chemistry related to this test has not been described, we provide the route from the alkaloid to the final colourful compound, and also a new preparation of o-quinones from o-halo phenols.