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In organic chemistry, an azo coupling is an reaction between a diazonium compound (R−N≡N +) and another aromatic compound that produces an azo compound (R−N=N−R’).In this electrophilic aromatic substitution reaction, the aryldiazonium cation is the electrophile, and the activated carbon (usually from an arene, which is called coupling agent), serves as a nucleophile.
Azo dyes are synthetic dyes and do not occur naturally. [2] [3] Most azo dyes contain only one azo group but there are some that contain two or three azo groups, called "diazo dyes" and "triazo dyes" respectively. Azo dyes comprise 60–70% of all dyes used in food and textile industries. [3]
Azo compounds are organic compounds bearing the functional group diazenyl (R−N=N−R′, in which R and R′ can be either aryl or alkyl groups).. IUPAC defines azo compounds as: "Derivatives of diazene (diimide), HN=NH, wherein both hydrogens are substituted by hydrocarbyl groups, e.g. PhN=NPh azobenzene or diphenyldiazene.", where Ph stands for phenyl group. [1]
The increased hydrophilicity of Glycoazodyes allows for the elimination of surfactants, mordants, and salts, during the dyeing process and permits the aqueous dying of a variety of textiles at moderate temperatures and pressures. The unique structure may also allow for the treatment of textile effluent through biological means.
The most common type of coupling reaction is the cross coupling reaction. [ 1 ] [ 2 ] [ 3 ] Richard F. Heck , Ei-ichi Negishi , and Akira Suzuki were awarded the 2010 Nobel Prize in Chemistry for developing palladium-catalyzed cross coupling reactions .
Azo violet (Magneson I; [1] p-nitrobenzeneazoresorcinol) is an azo compound with the chemical formula C 12 H 9 N 3 O 4. It is used commercially as a violet dye and experimentally as a pH indicator , appearing yellow below pH 11, and violet above pH 13. [ 2 ]
A similar palladium cycle but with different scenes and actors is observed in the Wacker process. Heck Reaction Mechanism This cycle is not limited to vinyl compounds, in the Sonogashira coupling one of the reactants is an alkyne and in the Suzuki coupling the alkene is replaced by an aryl boronic acid and in the Stille reaction by an aryl ...
Cross-couplings are a subset of the more general coupling reactions. Often cross-coupling reactions require metal catalysts. One important reaction type is this: R−M + R'−X → R−R' + MX (R, R' = organic fragments, usually aryl; M = main group center such as Li or MgX; X = halide)