Of p-dimethylaminobenzaldehyde

Procedure. Transfer ca 0.2-g accurately weighed sample to a 100-ml vol flask and add distd w to the mark. Stopper and shake until completely dissolved. Pipette out 5 ml and add 1 ml of the reagent (prepd by dissolving 1 g of p-dimethylaminobenzaldehyde in 50 ml absol ale and 5 ml coned HCl). If hydrazinium ion is present, the soln turns yel at first and then, after 10-15 mins, intensely red-orange. Compare the intensity of coloration of similarly treated solns (standards) contg 0.0001 mg to 1 mg of NaH4 per ml... 

The reaction can be monitored by TLC (CHgCl2). The spots were developed with an ethanolic solution of p-dimethylaminobenzaldehyde/HCl. The product gave a bright red spot at Rf 0.5 and the imidate ester gave a yellow spot at Rf 0.6. Addition of small portions of diethyl oxalate/potassium ethoxide complex was continued if the starting material was not consumed after the initial reaction period. 

Dissolve 0.125 g of p-dimethylaminobenzaldehyde in 65 ml of concentrated sulphuric acid and 35 ml of water. Add 7 ml of this reagent by burette to an aliquot of a dilution of the sample in chloroform to contain between 0.6 and 7-5 mg of camphor. Stopper, shake and allow to stand two hours for colour development and measure the extinction at U60 m. ... 

WARNING Paper soaked in alcoholic or carbon tetrachloride solution containing 10% of a mixture of equal parts of p-dimethylaminobenzaldehyde and colorless diphenylamine, and then dried, will turn from yellow to deep orange in the presence of approximately the maximum allowable concentration of phosgene, and should always be used where the generation of this gas is possible or suspected. See also Braker and Mossman. 

Add 2 ml of 95% ethanol to each vial. Slowly add 0.5 ml of p-dimethylaminobenzaldehyde reagent to each vial. The reaction may bubble vigorously as this is done, so use caution so as not to lose your samples. 

A reduction by formaldehyde is involved in the first step of the preparation of p-dimethylaminobenzaldehyde (5) from p-nitrosodimethylaniline (1), dimethylaniline... 

Qualitatively, the presence of the nonulosaminic acids is best indicated by the brilliant-red coloration formed on addition of an acidic solution of p-dimethylaminobenzaldehyde (the so-called direct Ehrlich reaction ), and by the bright-purple coloration which develops upon boiling with Bial s reagent for several minutes at 100°. In addition, the nonulosaminic acids give a blue-violet coloration with Dische s diphenylamine reagent for deoxypentoses and a positive reaction in the tryptophan-perchloric acid test. Since no single one of these color reactions is absolutely specific for a nonulosaminic acid, it is advisable to carry out at least two of these for a qualitative analysis. For quantitative determinations, all four reactions have been employed, using either A/ -acetylneuraminic acid (m. p., 183-185° [a] —32.0°) or methoxyneuraminic acid [m. p., 200° (dec.) [a]o —55.0°] as colorimetric standards. 

Under standard conditions, a 6% solution of p-dimethylaminobenzaldehyde in mineral acid is added to the sample, and the mixture is heated for 30 min. at 100 . The developed coloration, with Xmax at 530 and 565 m i, is then read at 565 m/i it is stable for several hours. The method will give incorrect results in the presence either of pyrrole derivatives or of alkali-treated mucopolysaccharides. 

Wessely and co-workers [90] have applied TLC on a preparative scale instead of fractional distillation in order to isolate the hydro-quinone acetate formed during treatment of hromo phenols with lead tetraacetate. They worked with benzene on silica gel G layers and visualised by spraying with diazotised sulphanilic acid or a I % solution of p-dimethylaminobenzaldehyde (Rgt. No. 72). 

Takacs [85] has separated the o- and p-benzoquinol acetates and o-quinone diacetate resulting from oxidation with lead tetraacetate of phenols containing an o-isopropyl, sec-butyl or tert.-butyl group. The o-derivatives were separated and purified on silica gel G. A 1 % solution of p-dimethylaminobenzaldehyde in concentrated sulphuric acid was... 

EAs can be identified by various analytical methods. The most important colorimetric analysis is the reaction of EAs with van Urk s reagent, a mixmre of p-dimethylaminobenzaldehyde, FeCla, and H2SO4. This reagent is also used for quantification of EAs by measurement of the absorbance at 580 nm of the reaction products [59, 60]. 

B. 5% soln. of p-dimethylaminobenzaldehyde in hydrochloric acid-methanol (5 100) (Ehrlich s reagent)... 

This consists of p-dimethylaminobenzaldehyde in hydrochloric acid. It is used in the estimation of urinary urobilinogen (which gives a red colour), porphobilinogen, (giving a red colour which can be extracted into organic solvents) and indican (when the red chromogen can be extracted into alkali). 

Pipette 4 ml of this solution into a 100-ml graduated flask and into another 100-ml graduated flask pipette 2 ml of an accurately prepared 0 05 per cent solution of procaine hydrochloride in water. To each flask add 50 ml of a buffer solution (prepared by mixing 11 90 ml of 0-2M hydrochloric acid and 88 10 ml of 0 2M potassium chloride) and then add 5 ml of a 1 per cent solution of p-dimethylaminobenzaldehyde in 95 per cent ethanol (prepared not more than three days before use and stored in an amber-coloured bottle), dilute to volume with water and mix. 

Reagents 1% solution of p-dimethylaminobenzaldehyde in a mixture of 95 parts of ethanol and five parts of HCl or 1% aqueous NaN02 solution and 1% solution of resorcinol in 10% Na2C03 or 1% aqueous NaN02 solution, 1% ammonium sulfamate, and 0.1% N-l-naphthylethyl-enediamine dihydrochloride in water. 

They react with a solution of p-dimethylaminobenzaldehyde in an acid medium (p. 322), splitting off an acyl group and giving rise to azines ... 

Preparation of derivatives for chromatography To a solution of 0.5 mmole of sulfide in 2 ml of methanol a solution of 200 mg of sodium p-nitrobenzenesulfochloroamide in 5 ml of methanol is added and the reaction mixture is suitably acidified with one drop of 1% formic acid in methanol (to make the reaction smoother). The reaction is accompanied by decolorization of the yellow reaction mixture. After 15 min the reaction mixture is diluted with 20 ml of water and additioned with 10 ml of 2 N NaOH. It is then extracted twice with 5 ml of chloroform. The chloroform solution is applied directly onto the paper, a suitable amount being 5 to 15 ig. Detection is carried out by spraying the chromatogram with a solution of p-dimethylaminobenzaldehyde after previous reduction with stannous chloride (p. 154). Yellow spots on a white background are produced. 

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