Diazotization with alkali nitrite

A. Diazotization with Alkali Nitrite in Aqueous and Concentrated... 

Diazotization of Amines with Alkali Nitrite in Dilute Aqueous Mineral Acids... 

Pigment synthesis follows the typical route to azo pigment lakes the aniline derivative or the aniline sulfonic acid is diazotized with sodium nitrite in an acidic medium (hydrochloric acid), followed by coupling on the Naphthol AS derivative, which is initially dissolved in an alkaline solution and then precipitated by adding inorganic or acetic acid. If a Naphthol AS sulfonic acid is used as a coupling component, it must be neutralized with alkali for dissolution and coupled directly. 

Diazotetrazole was the first diazoazole synthesized by diazotization of diluted solutions of the aminotetrazole in hydrochloric acid with sodium nitrite subsequent neutralization with alkali was not necessary (1892LA46). Diazotization with isoamyl nitrite in THF and aqueous hydrochloric acid was also effective and allowed the isolation of the diazotetrazole (72JA1379). When the aminotetrazole was diazotized with sodium nitrite in acetic acid, only the 1,3-ditetrazolyltriazene 250 was obtained (10CB1866). 

The effectiveness of the antimicrobial activity can be enhanced by combining zinc citrate with triclosan [22-24]. Triclosan, or 2,4,4 -trichloro-2-hydroxy diphenyl ether, is an aromatic, trichlorinated synthetic componnd. It can be obtained by reaction of 2,4-dichlorophenol with 2,5-dichloronitrobenzene in the presence of alkali and reduction of the 2,4,4 -trichloro-2 -nitrodiphenyl ether into 2,4,4 -trichloro-2 -aminodiphenyl ether. This is diazotized with sodium nitrite with excess sulfnric acid. After hydrolization, 2,4,4 -trichloro-2 -hydroxydiphenyl ether is extracted with xylene and purified [20-25]. 

Diazotization, coupling, and methylation may be combined in a one-pot process by dissolving the aromatic amine and the heterocyclic methylene base in an organic acid and effecting the simultaneous diazotization and coupling by addition of sodium nitrite. The dye base is released by addition of alkali and is methylated with dimethyl sulfate to form the alkylarylhydrazone dye (e g., 11) [27]. 

A solution of 40 g. (0.30 mole) of m-aminoacetophenone (p. 7) in 122 ml. of 36% aqueous hydrobromic acid and 120 mb of water is diazotized by treatment at a temperature below 0 , with a solution of 21.2 g. (0.31 mole) of sodium nitrite in 36 ml. of water. Sulfur dioxide is passed into a solution of 54.2 g. of copper sulfate and 27.2 g. of potassium bromide in 250 ml. of water until reduction is complete. Tbe resulting solution of cuprous bromide is added to tbe diazonium salt solution, and after being beated in a water batb for a short period tbe mixture is steam-distilled. The m-bromoacetophenone is extracted from the distillate with ether, and the ethereal solution is washed with dilute alkali, dilute acid, and water. Drying the resulting solution and distilling gives a 54% yield of product, b.p. 131°/16 mm. 

A mixture of 50 g. (0.35 mole) of 2-naphthylamine, 670 ml. of water, and 140 ml. of concentrated hydrochloric acid is diazotized at 0-10° in the usual manner by the addition of 20% aqueous sodium nitrite solution. To the resulting solution of the diazonium salt is added with stirring a cold suspension of mercuric bromide formed by treating 57 g. (0.175 mole) of mercuric nitrate with 83 g. (0.80 mole) of sodium bromide in a total volume of 250 ml. of water. The precipitated yellow complex is removed by filtration, washed with water and acetone, and air-dried. It weighs 137-149 g. The solid is mixed well with 300 g. of powdered sodium bromide, and the mixture is added in several portions to a reflux apparatus heated to 90° in an oil bath. Vigorous evolution of gas follows the addition of each portion. After decomposition is complete, the reaction mixture is extracted with benzene and the benzene solution is washed with dilute acid and alkali. Removal of the solvent followed by two distillations of the residual oil gives a product boiling at 103-104°/4 mm. After one recrystallization from a mixture of 110 ml. of hot ethanol and 4 ml. of water, 38-43 g. (53-59%) of colorless plates of 2-bromonaphthalene, m.p. 55-56.4°, is obtained. 

Arylamines that contain an acid group (sulfo or carboxyl) are diazotized by the so-called indirect method . They are dissolved in aqueous alkali, treated with a solution of the calculated amount of sodium nitrite, and dropped into an excess of acid the diazonium salt then usually separates as a solid. This method has been used with success for diazotizing aminobenzoic acid and aniline- and naphthylamine-sulfonic acids weakly basic amines such... 

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