Anomalous behavior of aminohydroxynaphthalenesulfonic acids during diazo coupling

The effect of pH on the diazo coupling reaction of some commonly used coupling components (J-acid, Gamma acid, H-acid and S-acid) with monosubstituted diazobenzenes has been investigated. The results demonstrate that, contrary to previous reports, selective diazo coupling ortho to an amino group of...

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Bibliographic Details
Published in:Dyes and pigments 1986, Vol.7 (3), p.215-230
Main Authors: Freeman, Harold S., Whaley, Wilson M., Esancy, Michelle K., Esancy, James F.
Format: Article
Language:English
Subjects:
Applied sciences
Chemical industry and chemicals
Dyes, pigments
Exact sciences and technology
Industrial chemicals
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Summary:The effect of pH on the diazo coupling reaction of some commonly used coupling components (J-acid, Gamma acid, H-acid and S-acid) with monosubstituted diazobenzenes has been investigated. The results demonstrate that, contrary to previous reports, selective diazo coupling ortho to an amino group of an aminohydroxynaphthalenesulfonic acid does not occur in weakly acidic (pH 5–6) media. In fact, such media were found to give nearly exclusive diazo coupling ortho or para to the hydroxyl group. The desired amine coupling reactions required a pH of 3.0–3.5 and occurred only with the more reactive diazonium salts. The structures of the dyes obtained were unambiguously determined with the aid of 1H-NMR spectroscopy.
ISSN:0143-7208
1873-3743
DOI:10.1016/0143-7208(86)85010-0