Patent GB-585781-A (GB)
Title: Improvements in or relating to the production of azo dyestuffs
IPC: C09B27/06
Filed: 1944-12-01
Abstract: Azo dyestuffs are manufactured by reacting a diazonium compound with a compound of the formula <FORM:0585781/IV/1> wherein R1 and R2 represent the same or different groups -COOR, -CN, -COR or -CONHR, and R and R3 represent hydrogen or hydrocarbon or substituted hydrocarbon groups and may be the same or different, the reaction being effected in the presence of strong alkali (e.g. caustic soda, caustic potash or sodium ethoxide) and the diazonium compound being present in a proportion of at least two molecular equivalents (calculated with regard to the number of diazo groups present) per molecular equivalent of the other reactant.  The diazonium compound may be derived from a monoamine, in which case the reaction takes place in accordance with the equation <FORM:0585781/IV/2> wherein R4 is an aryl, substituted aryl or heterocyclic residue and Y is an acid grouping.  Alternatively, diazonium compounds containing more than one diazo group may be employed, in which case the minimum molar proportion thereof is correspondingly reduced, and the formula of the products is modified, those from tetrazotized diamines being of the type <FORM:0585781/IV/3> where x is a positive integer.  When the group R2 in the product is an ester group it may be subsequently hydrolysed to a free carboxylic acid group.  The products may be purified from any concurrently formed pyrazole-5-one by virtue of their lower solubility in alkali.  In examples: (1) sulphanilic acid is diazotized and reacted with a solution of ethyl acetosuccinate in aqueous caustic soda, and the product is hydrolysed with caustic soda solution to produce tartrazine; (2) a -naphthylamine is diazotized and reacted with ethyl acetosuccinate in caustic soda solution, yielding 4-a -naphthylazo-1-a -naphthyl-3-carbethoxy-5-pyrazolone; (3) the a -naphthylamine in (2) is replaced by b -naphthylamine; (4) by p-amino-benzenesulphonamide, and (5) by aminoazobenzene; (6) aniline is diazotized and reacted similarly with ethyl b  : b -diacetylpropionate, (7) with ethyl cyansuccinate, and (8) with ethyl acetosuccinate o-chloranilide; (9) 2-naphthylamine-1-sulphonic acid sodium salt, and (10) p-aminobenzoic acid are diazotized, and reacted as in (2); (11) p-nitraniline is diazotized and reacted as in (1) (including the hydrolysis step); (12) 2-naphthylamine-4 : 8-disulphonic acid is diazotized, and reacted as in (2); (13) 1 : 5-diaminoanthraquinone is tetrazotized and reacted with an equimolecular proportion of ethyl acetosuccinate in caustic soda solution; (14) dehydrothio-p-toluidine is diazotized, and reacted as in (2); (15) benzidine is tetrazotized and reacted with an equimolecular proportion of ethane-a  : a  : b -tricarboxylate or ethyl acetosuccinate (the same product being obtained in either case). Additional starting materials specified are, on the one hand, the diazonium or tetrazonium compounds from toluidines, xylidines, naphthionic acid, p-aminobenzyldimethylamine, m-aminophenyldimethylamine, m-nitraniline, p-aminophenol, aminonaphthol-sulphonic acids, aminoazobenzenesulphonic acids, tolidines, p : p1-diaminostilbene, p : p1-diaminodiphenylamine, 2 : 7-diaminofluorene, 2 : 7 - diaminocarbazole, p : p1 - diaminoazo - benzene, p-phenylenediamine, 1 : 4- and 1 : 5-diaminonaphthalenes, and dehydrothio - p - toluidinesulphonic acid, and, on the other hand, ethyl aceto-succinate anilide.  Ethyl acetosuccinate o-chloranilide is obtainable by interaction of equimolecular proportions of sodio acetoacet-o-chloranilide and ethyl chloracetate in ethyl alcohol.  Other starting materials of the formula <FORM:0585781/IV/4> p  may be obtained similarly, as described in Specification 585,780.