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Formation rates and protonation constants of azo dyes in a sodium dodecylsulphate micellar solution
J S Romero1, M C Alvarez-Coque, G R Ramos
1Departamento de Química Analítica, Facultad de Química, Universitat de Valencia, 46100 Burjassot, Valencia, Spain.
Abstract:
The effects of a sodium dodecylsulphate micellar solution on the coupling rates of several diazotizated arylamines with N-(1-naphthyl)-ethylenediamine and the shifts in the protonation constants of the corresponding azo dyes are quantitatively studied. Aniline, o-, m- and p-aminobenzoic acids, ethyl p-aminobenzoate and several sulphadrugs are used, and the relationships among the intensity of the effects and the molecular structure of the diazonium ions and the dyes are discussed. A single simplified procedure for the determination of all the substances at pH = 1.3 +/- 0.3, where coupling is quickly completed to directly produce the protonated form of the dyes, is established and applied to the analysis of several pharmaceutical preparations.
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