Diazo benzene

Phenyl Nitroso Amine.—Under certain conditions aniline, a primary aromatic amine, apparently undergoes this same reaction and yields a nitroso amine. If the potassium salt of diazo benzene, which is obtained from aniline by the action of nitrous acid and which will be explained later (p. 591), is heated, a change takes place involving space relations. The product is isomeric with the diazo compound and is known as the... 

By more cautious oxidation with mercuric oxide, copper sulphate or ferric chloride, the salts of phenyl hydrazine yield salts of diazo benzene. 

The details of this reaction and the one following will be considered later in duscussing the constitution of diazo compounds. The reaction always takes place in an acid solution, i.e., with the salt of the amine, so that the product obtained is not the diazo benzene as written above, but the salt of it. 

Diazo Benzene, CeHs—N2—OH Benzene Diazonium Chloride, CeHs—Ns—Cl... 

Constitution.—In the following discussion of the constitution and reactions of diazo compounds diazo benzene and its salts will be taken as examples. The reactions, however, are to be considered as typical of all diazo compounds. The physical properties of free diazo com-... 

Bases, Neutral Salts.— As a base it forms salts, in which form the diazo compound is obtained by diazotization, and which though also unstable has been isolated in small quantities and the composition and properties determined. Of the three salts, the sulphate, chloride and nitrate, the first is the most stable and the last is the least stable. They are colorless crystalline neutral compounds soluble in water, difficultly soluble in alcohol and insoluble in ether. After being prepared by the ordinary diazo reaction, with sodium nitrite in cold acid water solution, they may be precipitated in crystalline form by the addition of alcohol and ether. If the diazotization is effected in alcohol solution by means of amyl nitrite or ethyl nitrite the crystals of the diazonium salt separate at once. These salts of diazo benzene all show true salt characteristics, e.g., they lower the freezing point of solutions. The diazo radical, (CeHs—N2—) is thus basic toward strong acids, and the hydroxide, the non-isolated hypothetical diazo benzene, CeHs—N2—OH, is the free base. It may be considered as the simplest aromatic diazo compound and the mother substance of all other members of the class. 

What now is the constitution of these diazo compounds The facts thus far considered and which must be explained by an accepted constitutional formula are, (i) Their formation by the action of nitrous acid on a primary- amine, (2) Their conversion into azo, amino azo, hydroxy azo and hydrazine compounds and (3) the basic character of the hydroxy compound, diazo benzene, and the true salt character of the compounds formed with strong acids. 

Kekule Formula.—These facts led Kekule to suggest a second formula in which the nitrogen atoms are both trivalent and in the same relationship to each other and the ring as they are in azo benzene. The formula is CeHs—N=N—Cl, benzene diazonium chloride. For some time this was the accepted formula for, if we put it in the reactions which we have written for the formation of diazo compounds and for their conversion into azo compounds and into hydrazines, we find that it is satisfactory. It does not agree, however, with the true salt character of benzene diazonium chloride nor the strongly basic nature of the hydroxide compound, the free diazo benzene. In every respect the neutral salts, e.g., benzene diazonium chloride and the free diazo... 

Such a reaction agrees perfectly with the new formula which has been generally accepted as expressing the constitution of the free diazo base and the salts. The base thus takes the name benzene diazonium hydroxide and the salts, e.g., the chloride, benzene diazonium chloride signifying their ammonium character. The new formula does not, however, fit the reactions by which diazo. compounds are converted into azo or amino azo compounds nor the reduction of diazo benzene to phenyl hydrazine. Thus we have two formulas neither of which... 

Acids, Alkali Salts.—The free diazo benzene base which will always be spoken of now as benzene diazonium hydroxide and which necessitates the introduction of the pentavalent nitrogen formula is formed by the action of silver hydroxide upon benzene diazonium chloride. By the action of acids the diazonium hydroxide is converted into salts and these salts are neutral. If, however, the diazonium chloride is treated with alkalies, like potassium hydroxide, we obtain alkali metal salts of the diazo compound. 

A] Diazotization Reactions. There exists a marked and pronounced difference between the aliphatic amines and the primary aromatic amines whereby the former reacts with cold aqueous nitrous acid (HNOg) to give rise to the formation of the corresponding primary alcohol as the major product of reaction and the latter under identical experimental parameters exclusively results into the formation of benzenediazonium chloride (salt), sometimes also termed as diazo-benzene chloride as illustrated below ... 

Classification Diazo benzene salt Empirical Ci Hi2N 0 Formula C12H10N3CH2O Uses Sensitizer for silk screen emulsions Trade Name Synonyms Diazon-8 [Molecular Rearrangement]... 

Fischer discovered phenylhydrazine in 1875. Strecker by treating diazo-benzene nitrate with excess of potassium hydrogen sulphite, obtained a salt... 

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