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Effect of alkali on methylene blue (C.I. basic blue 9) and other thiazine dyes

Mills, A. and Hazafy, D. and Parkinson, J. and Tuttle, T. and Hutchings, Michael G. (2010) Effect of alkali on methylene blue (C.I. basic blue 9) and other thiazine dyes. Dyes and Pigments, 88 (2). pp. 149-155.

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Abstract

A detailed study of the action of alkali on methylene blue (C.I. Basic Blue 9) and other thiazine dyes was carried out through a combination of UV/visible spectroscopy, thin layer chromatography, mass and NMR spectrometry and computational methods. In 0.1 M aq alkali solution, methylene blue forms a highly coloured, lipophilic species that is mainly Bernthsen's methylene violet i.e. a hydrolysis decomposition product, this being contrary to the report of a red N-hydroxy methylene blue adduct. The nature of the heterocyclic nitrogen atom in C.I. Basic Blue 9 is discussed and it is concluded there is no basis for the proposal of nucleophile addition at this site of the dye. In contrast, other thiazine dyes are deprotonated by alkali to form their neutral, highly coloured, lipophilic conjugate base forms.

Item type: Article
ID code: 27752
Keywords: methylene blue, hydrolysis, thiazine, C.I. basic blue 9, methylene violet, DFT, Physical and theoretical chemistry, Chemical Engineering(all), Process Chemistry and Technology
Subjects: Science > Chemistry > Physical and theoretical chemistry
Department: Faculty of Science > Pure and Applied Chemistry
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Depositing user: Mrs Roslyn MacDonald
Date Deposited: 16 May 2011 12:00
Last modified: 27 Mar 2014 08:58
URI: http://strathprints.strath.ac.uk/id/eprint/27752

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