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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.
Diazonium compounds or diazonium salts are a group of organic compounds sharing a common functional group [R−N + ≡N]X − where R can be any organic group, such as an alkyl or an aryl, and X is an inorganic or organic anion, such as a halide. The parent compound where R is hydrogen, is diazenylium.
The Gomberg–Bachmann reaction, named for the Russian-American chemist Moses Gomberg and the American chemist Werner Emmanuel Bachmann, is an aryl-aryl coupling reaction via a diazonium salt. [1] [2] [3] The arene compound (here benzene) is reacted with a diazonium salt in the presence of a base to provide the biaryl through an intermediate ...
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 nucleophilic addition of the enolate anion 2 to the diazonium salt produces the azo compound 3. Intermediate 3 has been isolated in rare cases. However, in most cases, the hydrolysis of intermediate 3 produces a tetrahedral intermediate 4 , which quickly decomposes to release the carboxylic acid 6 .
The Griess test involves two subsequent reactions. When sulfanilamide is added, the nitrite ion reacts with it in the Griess diazotization reaction to form a diazonium salt, which then reacts with N-(1-naphthyl)ethylenediamine in an azo coupling reaction, forming a pink-red azo dye.
Of considerable practical value in the dye industry are the diazo coupling reactions. The reaction of phenyldiazonium salts with aniline gives 1,3-diphenyltriazene. [3] The structure of the salt has been verified by X-ray crystallography. The N-N bond distance is 1.083(3) Å. [4]
The Meerwein arylation is an organic reaction involving the addition of an aryl diazonium salt (ArN 2 X) to an electron-poor alkene usually supported by a metal salt. [1] The reaction product is an alkylated arene compound. The reaction is named after Hans Meerwein, one of its inventors who first published it in 1939. Meerwein arylation