On the Dimerization of Morphine by Tetraaminocupric Sulphate
Department of Organic Chemistry, Faculty of Chemistry, National Autonomous University of Mexico, Mexico City (CDMX), Mexico.
Research Article
International Journal of Scholarly Research in Chemistry and Pharmacy, 2025, 05(01), 001-004.
Article DOI: 10.56781/ijsrcp.2025.5.1.0021
Publication history:
Received on 01 April 2025; revised on 05 June 2025; accepted on 07 June 2025
Abstract:
Lindo proposed an assay for identification of morphine using copper sulphate and aqueous ammonia. In the presence of morphine an emerald-green colour is obtained.
In this communication the chemistry of this test is provided. The principal reaction site in morphine is the phenol at C-3 which forms the phenolate in alkaline medium. This anion is in resonance with a carbanion at C-2. This is less stable and therefore more reactive. The cupric ion accepts four ligands, in this case four NH3 molecules. Copper (II) is an electron acceptor passing to cuprous ion. Thus, the electrodotic carbanion transfers one electron to the metal (redox step). The remaining free electron in the organic molecule couples with another similar species. The dimer obtained is transoid in order to eliminate steric hindrance between the two dienones.
Finally, aromaticity is restored by enolization and 2,2’bimorphine is obtained. The observed colour in the test is due to halochromism, not to an inorganic product.
Keywords:
Carbanion; Cuprammonium Sulphate; Electron Acceptor; Electron Coupling; Electron Donor; Halochromism
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