On the reaction mechanism of a colour test for uracil detection
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, 2025, 07(01), 001-004.
Article DOI: 10.53346/wjcps.2025.7.1.0024
Publication history:
Received on 24 September 2025; revised on 10 November 2025; accepted on 13 November 2025
Abstract:
When uracil is dissolved in bromine water and excess of a solution of barium hydroxide is added, a purple precipitate or colour is developed. It was found that iso-dialuric and dialuric acid form purple precipitates with barium hydroxide. Besides, crystalline alloxanthine was isolated from a purple precipitate by elimination of barium with dilute sulphuric acid. These facts suggest a reaction route. In this communication we provide the reaction mechanism of the series of reactions leading to the key products. In acidic medium, there is double bromination at ipso-carbon. Then, in alkaline medium, a nucleophilic reaction gives rise to a gem-diol, whose dehydration forms iso-dialuric acid (first target molecule). The isomerization of this compound to dialuric acid is interesting because it seems a hydride transfer. However, there is an acidic hydrogen that permits formation of an enediol which is apt for a concerted push-pull mechanism, initiated by a hydroxyl ion. This way the second target molecule is obtained. Partial aerial oxidation of dialuric acid to alloxan and combination of these compounds yields alloxanthine (third target molecule).
Keywords:
Alloxan; Alloxanthine; Dialuric Acid; Enediol; Iso-Dialuric Acid; Uracil
Full text article in PDF:
Copyright information:
Copyright © 20251 Author(s) retain the copyright of this article. This article is published under the terms of the Creative Commons Attribution Liscense 4.0