Patent GB-761054-A (GB)
Title: Improved process for the manufacture of diazo compounds and derivatives thereof
Inventor: STACEY MAURICE
Filed: 1953-03-05
Abstract: Diazonium salts of perhalo-aliphatic acids are made by diazotizing a primary amine with an alkali metal nitrite and a perhalo-aliphatic carboxylic acid.  The diazonium salt, e.g. a trifluoroacetate, may be precipitated and sometimes may also be obtained by the addition of a perhaloacid e.g. trifluoroacetic acid, to a solution of a diazonium chloride.  The perhaloderivatives are probably double salts of the types RN2+ - OOCCF3.CF3COOH.  Other specified acids are trichloroacetic, heptafluorobutyric, tetrafluorosuccinic, perfluoroadipic, perfluorocaproic and perfluoroglutaric acids. Solid diazonium salts of perfluoro acids are stable.  The diazonium salts of perhalo acids participate in the usual reactions of diazonium salts and the diazonium group may therefore be replaced by halogen, cyanide and hydroxy groups and azo derivatives may be formed on coupling with phenols or amines (see Group IV(c)).  An aqueous solution of one of the salts, or the solid form, stirred with an aromatic compound yields a diaryl product by the linking together of the two aromatic nuclei.  Thus p-chlorobenzene diazonium trifluoroacetate and benzene yield 4-chlorodiphenyl.  The salts may also be made by treating N-acylamines with mixtures of perhalo acid anhydrides and alkyl or metallic nitrates.  In this modification ethyl and amyl nitrites and sodium nitrite may be used with trifluoroacetic anhydride to diazotize acetanilide or trifluoroacetanilide.  In examples: (1) acid diazonium trifluoroacetates are made from p-toluidine, and its diazonium chloride, mesidine, 2,4-dimethylaniline, p-chloroaniline and p-bromoaniline; (2) acid diazonium heptafluorobutyrates are made from p-toluidine, aniline and p-chloroaniline; in (3) and (4) p-toluidine is treated with sodium nitrite and perfluoroadipic and trichloroacetic acids respectively to yield the corresponding acid diazonium salts; in (5) benzene acid diazonium trifluoroacetate is heated to yield phenol, acid toluene-p-diazonium trifluoroacetate yields p-iodotoluene and p-tolunitrile when treated with aqueous potassium iodide and cuprous cyanide respectively, and benzidine acid tetrazonium trifluoroacetate with hypophosphorous acid yields diphenyl; in (6) acetanilide and its p-chloroderivative with amyl nitrite and trifluoroacetic anhydride yield diphenyl and 4-chlorodiphenyl respectively; (7) trifluoroacetanilide with ethyl nitrite and trifluoroacetic anhydride yields diphenyl; and in (8) solid acid p-toluene diazonium trifluoroacetate with benzene yields 4-methyldiphenyl.  Specification 659,897 is referred to.ALSO:Azo dyes are made by diazotizing a primary amine with an alkali metal nitrite and a perhalo - aliphatic carboxylic acid and coupling with a coupling component.  The diazonium salt may be isolated before coupling.  In modifications of the process the perhalo - acid may be added to a diazonium chloride to yield the diazonium perhalo acid sal or the N - acylated amine may be treated with an organic or metallic nitrite in the presence of an anhydride of the perhalo acid. Specified organic nitrites are ethyl and amyl nitrites.  Specified perhalo acids are trichloro - and trifluoro - acetic, heptafluorobutyric, tetrafluorosuccinic and perfluoroadipic, - and - glutamic acids.  In examples (1) acid p - toluene -, mesitylene -, 2, 4 - dimethylbenzene -, p - chlorobenzene and p - bromobenzene - diazonium trifluoroacetates, (2) acid p - toluene -, benzene and p - chlorobenzene diazonium heptafluorobutyrates, (3) acid p - toluene diazonium perfluoroadipate, (4) acid p - toluene diazonium trichloroacetate and (5) acid p - toluene diazonium trifluoroacetate with alkaline b  - naphthol yield the appropriate dyestuff and in (7) trifluoroacetanilide is treated with ethyl nitrite and trifluoroacetic anhydride and the product, without isolation, is coupled with alkaline b  - naphthol to yield phenyl azo - b  - naphthol.  Specification 659,897 [Group IV(b)] is referred to.