The mechanism of Mecke’s test for opioids
Department of Organic Chemistry, Faculty of Chemistry, National Autonomous University of Mexico, Mexico City (CDMX), Mexico.
Research Article
World Journal of Chemical and Pharmaceutical Sciences, 2023, 02(01), 023–027.
Article DOI: 10.53346/wjcps.2023.2.1.0014
Publication history:
Received on 12 December 2022; revised on 25 January 2023; accepted on 27 January 2023
Abstract:
Mecke colour test is an official assay for opioids, either for opium or for purified compounds. It employs a solution of selenious acid in sulphuric acid. However, organoselenium chemistry was misunderstood for many years. The reaction mechanism involving selenium (IV) compounds was explained by way of electron back donation, which is a theoretical contravention. In this communication we provide the reactions that take place during this test. Each step is fully commented and the electron flow is given. The reaction proceeds by way of an enol selenite. Acidolysis gives rise to a reduced selenium (II) intermediate and an activated ketone at C-2, that is, a redox reaction with polarity inversion. Addition of selenious acid and further electron shifts affords morphine ortho-quinone and elemental selenium.
Keywords:
Electron back donation; Polarity inversion; Reaction mechanism; Reactive intermediates; Redox reactions; Selenious acid
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Copyright © 2023 Author(s) retain the copyright of this article. This article is published under the terms of the Creative Commons Attribution Liscense 4.0