Insight into the mechanism of the Froehde test for morphine
Department of Organic Chemistry, Faculty of Chemistry, National Autonomous University of Mexico, Mexico City (CDMX), Mexico.
Research Article
Magna Scientia Advanced Research and Reviews, 2022, 06(02), 001–004
Article DOI: 10.30574/msarr.2022.6.2.0071
Publication history:
Received on 26 Septmber 2022; revised on 03 November 2022; accepted on 06 November 2022
Abstract:
The Froehde reaction for morphine employs a solution of sodium molybdate in concentrated sulphuric acid. This test has been extended to other alkaloids giving different colours. In this communication we present an insight into the reaction with morphine. It has the particularity that it does not invoke the concept of electron back donation since this known point of view reverses the normal polarization of a functional group. This route is based on a novel theoretical finding: the activation of a mixed ester (organic-inorganic) by means of protonation and water loosening. This causes Umpolung (polarity inversion) at ortho position, favouring a nucleophilic attack instead of the electrophilic one due to the original phenol group in morphine. The final part of the route to morphine ortho-quinone goes smooth via a six member concerted mechanism.
Keywords:
Activated ester; Bimolybdene pentoxide; Electron back donation; Molybdene blue; Molybdene dioxide; Reactive intermediates
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