P-Nitroaniline diazotized

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). 

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. 

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. 

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. 

F=fluorescence Q=quenching DSA = diazotized sulfanilic acid DNA = diazotized p-nitroaniline. 

Detection Spray with diazotized p-nitroaniline followed by aqueous NaOH to produce blue and purple spots, respectively. 

Derivation Diazotized p-nitroaniline is coupled with resorcinol. 

The determination of phenols according to VDI3485, Part 1 (1988) is a sum method. The phenolic compounds react on diazotized p-nitroaniline to produce an azo dye (see Eq. 7). In the first step of the reaction, a diazonium ion is formed from p-nitroaniline and sodium nitrite in acidic solution. This diazonium ion is a strong electrophilic reagent and attacks phenol in the para position with formation of an azo coupling by substitution. 

According to a suggestion by Scudi and Buhs (1942), tocopherols which are not methyl-substituted in ii-position could be coupled at this site with diazotized aromatic amines. Quaife (1944) found that y-tocopherol can l)e coupled within a pH range of 4.5-11 with diazotized p-nitroaniline to a red dye with an absorption maximum at 520 m , whereas tocopherol does not couple. These two tocopherols ( an thus be quantitatively determined by colorimetry in presence of each other. On the other hand, the a- and /3-fractions in a mixture of a-, fi-, and y-tocopherol cannot be measured individually. Weisler et al. (1947) coupled y- and 5-tocopherol with the more stable diazotized o-dianisidine. They found that the color intensity of the two coupling products was dependent on pH, and they based on this observation their method of determining y- and 5-toeopherol individually. Colorimetric measurements are carried out in the one case in soda alkaline and in the other in potassium hydroxide solution. 

Diazotized p-nitroaniline (800 mg p-nitroaniline in a mixture of 250 ml water and 20 ml HCl 5 ml NaN02 added dropwise until solution is colorless)... 

Para red n. Pigment red 1 (12070). Series of red pigments made by coupling reactions involving diazotized p-nitroaniline and alkahne j -naphthol. Adjustments in shade are made by substituting part of the jS-naphthol. 

Amine antioxidants Diazotized p-nitroaniline. Mix 5 ml 0.5% p-nitroaniline in 2 N hydrochloric acid with 0.5 ml 5% sodium nitrite, until colourless and 15 min later add 15 ml 20% sodium acetate. ... 

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