P-Nitroaniline, diazotization

Dimethylaminocinnamaldehyde Ehrlich reagent Ferric chloride (3%) p-Nitroaniline, diazotized Sodium bisulfite, aqueous Ninhydrin... 

CgHgNa. While crystals m.p. 147 C, b.p. 267"C, darken rapidly in air. Prepared by reducing p-nitroaniline or aminoazobenzene. Oxidizing agents convert it to quinone derivatives, hence it cannot be diazotized with nitric acid. 

Amino-5-methylthiazole does not react with diazotized p-nitroaniline in solutions acidified with acetic or hydrochloric acid (391). 2-Amino-4,5-dimethylthiazole with the diazonium salts of para-substituted anilines, however, gives product 193, involving reactivity of the exocyclic nitrogen (Scheme 122) (399). 

The NH2 groups can be diazotized and reduced in the presence of thiosulphates and different metal ions. The effect of some metal ions, namely Fe ", Sn, Cu +, and Co on the graft yield of cotton modified with aryl diazonium groups via its reaction with 2,4-dichloro-6-(p-nitroaniline)-5-triazine in the presence of alkali and followed by reduction of nitro group was studied [4]. 

A fast and sensitive method for determination of 4-aminoantipyrine (164) consists of coupling this compound with diazotized p-nitroaniline in a F1A system and measuring spectrophotometrically at 380 nm. About 50 determinations per hour could be carried out LOD was 0.05 ppm (SNR 3), RSD 0.61% for 4 ppm and 0.27% for 50 ppm, with linearity up to 50 ppm353. 

The 1,5-Bis (o ), mp 209 (m.-), mp 244°, and (p-), mp 262° derivs were prepd by Braun Rudolph (Ref 2) by nitrating the parent compd with a l/l mist of fuming nitric acid + sulfuric acid on a water bath. Horwitz Gra-kauskas (Ref 4) prepd the l,5-Bis(p-dinitro) deriv by coupling diazotized p-nitroaniline with 1-acetyl-2-(4,-bromo benzoyl) hydrazine, separating the tetrazole following cyclization l-(m-Nitrophenyl)-5-(p-nitrophenyl)-tetrazole, crysts, mp 170° (Ref 2)... 

A methanol extract of the sample is prepared and chromatographed on a Silica Gel GF chrcmatoplate with ethyl acetate, methanol, ammonium hydroxide (100, 10, 10, v/v) mobile phase. The Rf comparison to a reference similarily chromatographed, the response to diazotized p-nitroaniline (imidazole nucleus detection), U.V. (254 nm), and I2 vapors serves to identify cimetidine. 

When a dilute solution of sodium hydroxide is added gradually to a solution of an aryldiazonium salt, such as diazotized p-bromoaniline or p-nitroaniline, a yellow solid is precipitated. The same yellow solid can be obtained by adding an acid to the sodium diazotates, RN2ONa, formed by addition of the diazonium salt to an excess of sodium hydroxide. These products, which are exceedingly unstable and explosive in the... 

A limitation of both methods is that the second component must be liquid at the temperature of-the reaction, which is 5-10° for the diazohydroxide reaction and room temperature or slightly higher for the nitrosoacetylamine reaction. Experiments with solid reactants in solution have not been very successful, because of the difficulty of finding a suitable solvent. The solvent should be neutral and immiscible with water, have a high solvent action and reasonably low boiling point, and be inert to the free radicals which result from the diazo compound. The last qualification is the most difficult one to satisfy. Of the solvents which have been tried, carbon tetrachloride and chloroform appear to be the most suitable.18 From diazotized aniline and biphenyl in these solvents, some p-terphenyl is obtained, and from diazotized p-nitroaniline and biphenyl a small amount of 4-nitro-4 -phenylbiphenyl is formed. In these reactions an appreciable amount of tfie aryl halide (chlorobenzene and p-nitrochlorobenzene) is produced as a by-product. In general, the yields of products obtained by coupling with reactants in solution are extremely low. 

Binks and Ridd164 have made a complete kinetic study of the reaction of indole with several diazotized amines (p-nitroaniline, p-chloroaniline, sulfanilic acid, and aniline). Only the reaction with p-nitrodiazonium salt exhibits a simple kinetic form (pseudo first-order reaction) in the other cases the kinetics appear to be due to the superposition of two reactions, a normal azo-coupling reaction and an autocatalytic side reaction that removes diazonium ions, but does not form azo compounds. 

Diazonium compounds other than phenyldiazonium chloride are also used, but to a smaller extent. Thus, in some plants, diazotized m-xylidine is used, but this appears to have no advantage since the diazonium solution is less stable. Diazotized p-aminoacetanilide, on the other hand, is used in certain cases because it couples more vigorously and gives a very stable solution (see chromotropic acid), o- and p-Nitroaniline are used less frequently. 

Diazotized p-Nitroaniline. Reacts with all phenols and amines. It must be kept in the dark, and after 1 to 2 days it gives a yellow color with soda alone, so care is necessary in its use. Diazotized o-chloroaniline can be used equally satisfactorily. 

It is to be noted that diazo compounds are much more strongly basic than the amines from which they are derived. A solution of diazotized p-nitroaniline, for example, can be diluted with water to any desired extent, or even neutralized with acetate, without setting the diazonium base free. The stability of the diazonium compound is much less under these conditions, however, than in strongly acid solution. 

The titration of Schaeffer salt and R salt is done most satisfactorily with diazotized p-aminoacetanilide in slightly alkaline solution (carbonate), that of C salt with diazotized p-nitroaniline in the presence of bicarbonate. In the case of mixtures, the difference between the two titrations gives a measure of the amount of G salt present. 

Instead of isolating the dye from p-nitroaniline, it can be coupled in soda solution at 5 C. with the cidculated quantity of diazotized aniline to produce tlie important dye, naplithol blue-black B (C), having the structure ... 

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