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AZO COMPOUNDS — the organic matters containing one or several azo-groups — N = N — connected with two hydrocarbon radicals. And. — the crystal bright red or orange substances of weak-basic character steady against effect of acids, the bases, and also to heating. And. are water-insoluble, but are easily dissolved in alcohol, benzene and many other organic solvents. Their coloring is caused by hl. obr. existence of chromophoric group — N = N — and also number and the nature of deputies of an aromatic group. And. are intermediate products of recovery of aromatic nitro compounds in aromatic amino compounds that created a possibility of their practical receiving, in particular recovery nitro - nitrozo-and azooxycompounds metals (Zn, Fe) in alkaline condition according to the scheme:

2ArNO 2 + 8H → ArN = NAr + 4H 2 O

or oxidation of primary amines pshokhloridy or permanganate according to the scheme:

2ArNH 2 + O 2 → ArN = NAr + 2H 2 O.

At oxidation in acid medium azooxycompounds are formed. By the most widespread method of receiving And. the method of azocoupling of aromatic diazo compounds with is aromatic amine or oxycompounds according to the scheme:

ArN 2 Cl + C 6 H 5 OH → ArN = NC 6 H 4 OH + HCl.

By this method receive many dyes.

Dyes of a row A. paint fabrics of plant or animal origin. The most known of them: n-aminobenzene (aniline yellow), methyl orange apply as dyes or indicators in analytical chemistry.

Some from And. (e.g., diazonium salts) at interaction with proteins the so-called azoproteins having yellow, orange or red coloring give. The hl participates in formation of azo-proteins. obr. aromatic ring tyrosine (see) and imidazolny ring histidine (see) protein:

Scheme of formation of azoproteins

Azoproteins have antigenic specificity (see. Antigens ), other than specificity of initial protein. At the same time initial specificity of protein depending on intensity of processing by compounds of diazonium can remain or disappear completely. Ability of azoproteins to formation of complexes protein — azoprotein, and also existence at them intensive coloring allow to use widely them for quantitative researches in the area immunochemistry (see).

Many from And. are cancerogenic; especially strong carcinogens are n-(M-dimetil-amino) - azobenzene and other derivatives of aminoazo-benzene. Toxic action And. it is studied poorly, however during the work with not cancerogenic And. in industrial conditions cases of professional poisonings are known. Toxic action is more often And. the hl is limited. obr. skin rashes, also only in rare instances observe dermatitis and eczemas. On a nek-eye to data, And. cause leukoses and leykozopodobny states.

See also Azoic dyes , Indicators , Schiff of the basis .

Bibliography: Harmful substances in the industry, under the editorship of N. V. Lazarev, p.1 — 2, L., 1971; Fizer L. and Fizer M. Organic chemistry, the lane with English, t. 2, M., 1970.

M. A. Cheltsova.