Azo coupling

The azo coupling (English :azo coupling) couples diazonium compound and other aromatic compounds and is an organic reaction to compose an azo compound. I am called the diazo coupling. By this electrophilic aromatic substitution, as for the aryl diazonium cation, 求電子剤, active arene are nucleophilic reagents [¹].

Table of contents

Diazotization

It becomes the diazonium salt after a reaction called the diazotization when I mix nitrous acid and aniline. It is important as a reaction for the pre-stage of the coupling that this makes an azo dye and substitutes the functional group of aromatic compounds.

Use of the reaction

Because conjugates increase than an original material, the product comes to absorb the light (visible light in particular) of the long wavelength more. As a result, the aromatic azo compound tends to consist of extended conjugated systems a bright color and is used a lot as dye [²].

In addition, it is applied to the composition of sulfa drugs such as the Prontosil.

Reaction example

Much reaction system is explained [³]; [⁴]. A diazo compound of the orange is provided when I react phenol with benzene diazonium chloride. In this reaction, a base becomes the catalyst [²].

 

The aniline yellow (English version) of the associated dye is composed by aniline and diazonium salt [²].

 

Naphthol is a general receptor. As an example, the Olga Nord brown of the dye composes it from aniline and 1-naphthol (English version).

 

Similarly, the dye of the tango is done when I couple 2-naphthol (English version) and benzene diazonium chloride.

Source

1. ^ Smith, Michael B.; March, Jerry (2007), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (6th ed.), New York: Wiley-Interscience, ISBN 0-471-72091-7, http://books.google.com/books?id=JDR-nZpojeEC&printsec=frontcover 
2. ^ ^{a b c} Klaus Hunger; Peter Mischke, Wolfgang Rieper, Roderich Raue, Klaus Kunde, Aloys Engel (2005). "Azo Dyes." Woolman industrial chemical encyclopedia (English version). ヴァインハイム: Willy VCH（English version）. doi: 10.1002/14356007.a03_245. 
3. ^ J. L. Hartwell and Louis F. Fieser, "Coupling of o-tolidine and Chicago acid," it is Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv2p0145 Coll. Vol. 2: 145.
4. ^ H. T. Clarke and W. R. Kirner, "Methyl red," it is Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv1p0374 Coll. Vol. 1: 374.

Allied item

• Diazonium compound
• Coupling reactions

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