Nitrosodimethylaniline

Dissolve 30 g. (31-5 ml.) of technical dimethylaniline in 105 ml. of concentrated hydrochloric acid contained in a 600 ml. beaker, and add finely-crushed ice until the temperature falls below 5°. Stir the contents of the beaker mechanically (or, less satisfactorily, with a thermometer) and slowly add [ca. 10 minutes) a solution of 18 g. of sodium nitrite in 30 ml. of water from a separatory funnel, the stem of which dips beneath the surface of the liquid. Maintain the temperature below 8° by the 

Transfer 30 g. of the hydrochloride to a 500 ml. separatory funnel, add 100 ml. of water and shake until a thin paste of uniform consistency is obtained add 10 per cent, aqueous sodium hydroxide solution in the cold with shaking until the whole mass has become bright green (the colour of the free base) and the mixture has an alkaUne reaction. Extract the free base by shaking with two 60 ml. portions of benzene (1). Dry the combined benzene extracts with a Uttle anhydrous potassium carbonate, and filter into a distiUing flask fitted with a water condenser. Distil off about half of the benzene, and pour the residual hot benzene solution into a beaker. Upon cooUng, the p-nitrosodimethylaniUne erystallises in deep green leaflets. Filter these off and dry them in the air. The yield of p-nitrosodimethylaniUne, m.p. 85°, from the hydrochloride is almost quantitative. 

Experiment.—On a small hand balance, having two sheets of paper counterpoised in the pans, weigh out equal quantities (about 0-5 g.) of quinone and quinol dissolve the two substances separately in warm water and mix the solutions. Magnificent green needles of quinhydrone crystallise almost at once. After some time collect them at the pump, wash with water, and dry between filter papers over calcium chloride in a non-evacuated desiccator. Boil a few of the crystals with water and smell the vapours. 

Dimethylaniline (40 g. 0 33 mole) is dissolved in 250 c.c. of approximately 5 N-hydrochloric acid (one part of concentrated acid and one part of water) in a filter jar (capacity 1 1.) The jar is immersed in ice 200 g. of ice are dropped in, and then with good stirring—preferably with a mechanical stirrer—a cold solution of 25 g. of sodium nitrite in 100 c.c. of water is run in gradually from a dropping funnel (Fig. 51, p. 146). The temperature should not rise above 5° and no nitrous gases should be evolved. After the mixture has stood for one hour the orange-yellow hydrochloride is filtered thoroughly at the pump and washed several times with dilute hydrochloric acid (say 2 N). The salt is sufficiently pure for subsequent 

Since it is best to use the moist preparation for the further experiments, the whole of the material is weighed and an aliquot portion is dried, first on porous plate and then in a vacuum desiccator ot else on the water bath, so that the yield can be determined. It amounts to over 90 per cent of the theoretical. 

The free base is obtained by rubbing the moist salt (5-10 g.) under sodium carbonate solution in a separating funnel and shaking with ether until the whole is dissolved. The beautiful emerald green solution is first concentrated on the water bath and then the solvent is allowed to evaporate from a flat dish exposed to the air. Large green plates of nitrosodimethylaniline remain. They melt at 80° and can be recrystallised from petrol ether (boiling point 60°-80°). 

The tertiary aromatic bases share with the phenols the property of taking up a nitroso-group in the p-position when treated with nitrous acid in acid solution. As was mentioned elsewhere (p. 307), this reaction may be compared to the coupling of these compounds with diazobenzene. 

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It is important in this preparation to avoid an excess of nitrous acid before coupling occurs, otherwise the excess of nitrous acid will react directly with the dimethylaniline, and the deep green p-nitrosodimethylaniline so formed will contaminate the methyl-orange. 

Isopropylidene and benzylidene hydrazones of selenazole unsubstituted in the 5-position react with p-nitrosodimethylanilines or p-nitrosodiethyl-anilines when heated in organic solvents in the presence of acetic acid or pyridine (49). Highly colored crystalline 2-hydrazono-5-(p-dialkylamino-phenylimino)selenazoles are recovered from the reaction medium (Table X-10). 

Nitrosodimethylaniline.—It is a peculiarity of the tertiary aromatic amines, which distinguish them fiom the corresponding aliphatic compounds, that they arc capable of reacting with nitrous acid. Here the nitroso-group replaces hydrogen in the para-position to the dimethylamino-group. 

Naphthalene, 216 Naphthalene picrate, 217 Naphthalene sulphonaie ofsodiiim, 218-/ J-Naphthol, 219 Naphthol yellow, 224 /i Naphthyl acetate, 222 /j-Naphthyl methyl ether, 220 /-Nitracetanilide, 153 w-Nitraniline, 154 /-Nitraniline, 153 Nitric acid (fuming), 22 NitroVienzene, 142 w-Nitrobenzoic acid, 200 Nitrogen, qualitative e rimation, 2 quantitative estimation, 13 Nitrophenol, 183 Nitrosohenzene, 146 /-Nitrosodimethylaniline, 157 Niirosoplienol, 159... 

Dimethylquinoxaline reacts with pyridine and iodine to form quinoxaline-2,3-bis(methylenepyridinium iodide) (55). Condensation of (55) with p-nitrosodimethylaniline in the presence of potassium carbonate yields the bis-(p-dimethylaminonitrone) (56) and this on acid hydrolysis gives quinoxaline 2,3-dialdehyde (57) in high over-all yield. The dialdehyde is also obtained by selenium dioxide oxidation of 2,3-dimethylquinoxaline. ... 

N-(p-Dimetliylaminophenyl)-Qr-(o-nitro-phenyl)nitrone from reaction of o-nitrobenzylpyridinium bromide and -nitrosodimethylaniline, 46, 82... 

Another reagent that convert benzylic halides to aldehydes is pyridine followed by /7-nitrosodimethylaniline and then water, called the Krohnke reaction. Primary halides and tosylates have been oxidized to aldehydes by trimethylamine N-oxide, and by pyridine N-oxide with microwave irradiation. ... 

Photoreactions on ZnO powder in aqueous suspension and in contact with gases have often been studied during the last few decades, and only a few aspects of this work are reviewed here. For example, nitrous oxide and methyl iodide were found to decompose when brought into contact at 20 °C with the illuminated surface of ZnO and nitrate, indigo carmine and p-nitrosodimethylaniline were found to be reduced in aqueous suspensions ZnO is of special interest as it is one of the standard electrode materials in conventional semiconductor electrochemistry and photo-electrochemistry Colloidal ZnO has not been available until recently. It... 

Tertiary aliphatic - aromatic amines, unlike those of the aliphatic series, react with nitrous acid with the formation of C-nitroso compounds the nitroso group enters almost exclusively in the para position if available, otherwise in the ortho position. Thus dimethylaniline yields -nitrosodimethylaniline ... 

Bors, W., Michel, C. and Saran, M. (1979). On the nature of biochemically generated hydroxyl radicals studies using the bleaching of p-nitrosodimethylaniline as a direct assay method. Eur. J. Biochem, 95, 621-627. 

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