Orthanilic acid, diazotized

It has been observed2 that the dropwise addition of an aqueous solution of potassium ethyl xanthate to a cold (0°) aqueous solution of diazotized orthanilic acid results in the immediate loss of nitrogen when a trace of nickel ion is present in the stirred diazonium solution.3 The catalyst can be added as nickelous chloride or simply by using a nichrome wire stirrer. When no nickel ion is added and a glass stirrer is employed, the diazonium xanthate precipitates and requires heat (32°) to effect decomposition. 

Phenols can be detected with diazotized orthanilic acid or dianisidine by spraying an ammoniacal silver nitrate solution, followed by exposure to ultraviolet light, or with a modified ferric ferricyanide reagent, and also by exposing the wet layer successively to nitrogen dioxide and ammonia vapors. 

Azo coupling of diazotized orthanilic acid with the sodium salt of IV-acetyl J acid (7-acetylamine-4-hydroxynaphthalene-2-sulfonic acid) (22) yields mainly coupling ortho to the hydroxy group. Substitution at both activated positions is significantly ster-ically hindered but ionization of the hydroxy group of (22) at higher pH causes additional electrostatic interaction on formation of the a-complex for substitution at the favoured position decreasing the rate of reaction. 

Diazosulfanilic acid, see D-00142 Diazotized orthanilic acid, in S-00040 Dibenzo-16-crown-5, D-00155... 

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