Diazoamino compounds, preparation

Attention has previously (see Diazonium Sails) been drawn to the fact that unless an excess of hydrochloric (or mineral) acid is used in the diazotisation process, coupling occurs between the diazonium salt and the amine to give diazoamino compounds. Thus phenyldiazonium chloride and aniline yield diazoaminobenzene. This substance may be conveniently prepared by dissolving two equivalents of aniline in three equivalents of hydrochloric acid, and adding one equivalent of sodium nitrite in aqueous solution followed by two equivalents of sodium acetate ... 

The formation of diazoamino compounds, on coupling ArN2 with primary amines, does not constitute a total preparative bar to obtaining products coupled on the benzene nucleus for diazoamino compounds (33) may be rearranged to the corresponding amino-azo... 

For preparative diazotisations it is important to use a sufficient excess of acid and to keep the temperature down. Two moles of acid are required for each mole of amine, one for salt formation and one for liberating the nitrous acid from the nitrite. As a rule 2-5-3-0 moles are used. The excess is required to prevent condensation of the diazonium salt with unchanged base to diazoamino-compound such condensations take place in a faintly acid medium. The test for unchanged amine, accordingly, consists in buffering the free mineral acid with sodium acetate, and so providing a solution faintly acid with acetic acid, under which conditions the diazoamino-compound is formed. The latter is decomposed by mineral acids into diazonium salt and amine salt, e.g. 

Triazatrimethines are prepared by alkylation of linear triazene groups (diazoamino compounds) connecting an aromatic ring with a heterocyclic radical containing nitrogen. Thus, diazotization of an aromatic amine and coupling with, for example, a 2-aminoben-... 

A-Coupling with diazonium salts occurs fairly readily in phenan-thridium salts bearing an amino group at C-8. Many diazoamino compounds have been so prepared in the search for trypanocides,344-348... 

Various types of dyes are prepared from dehydrothiotoluidine. The free base or its sulfonic acid is diazotized and coupled with various naph-tholsulfonic acids such as, for example, e acid (l-naphthol-3,8-disul-fonic acid). The resulting dye is characterized by its high purity of color and can be discharged to a pure white. Such red direct dyes are sold under various names, and are usually referred to as dyes of the erika red type. (Erika Z is the combination from dehydxothioxylidine and e acid. l-Naphthol-3,6-disulfonic acid gives a very similar dye.) In addition to the true azo dyes from dehydrothiotoluidine, two other products are made which are important yellow dyes. One of these dyes is the naphthamine yellow NN (also called chloramine yellow) (Kalle), formed from dehydrothiotoluidinesulfonic acid by oxidation with sodium hypochlorite. The other is thiazole yellow or Clayton yellow, which is made by combining the diazo compound of dehydrothiotoluidinesulfonic acid with a second molecule of the same compound to form a diazoamino compound. 

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