Action of Nitrous Acid

It reduces to 4-aminodimethylaniline and gives dimethylamine with hot sodium hydroxide solution. It is prepared by the action of nitrous acid upon dimethylaniline at 0 C. 

If, however, a tertiary amine has two alkyl groups and also an aryl group having the para position unsubstituted, then the action of nitrous acid is to insert the nitroso group directly into this para position. Dimethylaniline, for example, when treated with nitrous acid readily gives p-nitrosodimethyl-... 

The colorations produced in this reaction arise from the action of nitrous acid on the phenol, giving />-nitrosophenol (I) which then reacts with excess of phenol to form an indophenol (II) which is an acid-base indicator ... 

Action of nitrous acid. Dissolve 0 5 g. in a few ml. of dil. HCl. Add slowly 2 ml. of a 20% solution of sodium nitrite. A brisk effervescence takes place and almost colourless crystals of trimethylenetrinitrosamine, m.p. 105, separate out. 

Action of nitrous acid. To a few ml. of 20% NaNO, solution add a few drops of cold dil. acetic acid. Pour the mixture into a cold aqueous solution of glycine, and note the brisk evolution of nitrogen. NH CH COOH -h HNO2 = HO CH2COOH + N + H O. Owing to the insolubility of cystine in acetic acid use a suspension in dU. acetic acid for this test. In each case care must be taken not to confuse the evolution of nitrogen with any possible thermal decomposition of the nitrous acid cf. footnote, p, 360). 

M-Hexyl alcohol has been prepared by the reduction of ethyl caproate by means of sodium and absolute alcohoB alone or in anhydrous ammonia solution by the reduction of -caproamide by means of sodium and absolute alcohol by the reduction of -caproaldehyde by means of sodium amalgam in dilute sulfuric acid and by means of living yeast, It has also been produced by the action of nitrous acid upon w-hexylamine by the action of sodium upon a mixture of ethyl alcohol and M-butyl alcohol ... 

Dia2oaminoben2ene has also been prepared by the action of nitrous acid gas on aniline in alcohol by the action of silver nitrite on aniline hydrochloride and together with phenylurea by the action of nitrosophenylurea on aniline in methyl alcohol. Niementowski and Roszkowski have reported studies on the diazotization of aniline, aniline hydrochloride, and aniline sulfate with sodium nitrite and silver nitrite. The procedure described is adapted from that of Fischer. ... 

Phthalophenone is then converted successively into dinitro-, diainino-, and, finally, by the action of nitrous acid, into diliydr-oxyphthalophenone or phenolphthalein,... 

The action of nitrous acid on o-aminohydroxamie acids gave products that are believed to be triazine hydroxamic acids, e.g., 28. These gave a red color with ferric chloride, and 28 was converted by sodium hydroxide into o-azidobenzoic acid (29). 

The action of nitrous acid on the benzodiazepine A -oxide 38 gives the nitrosoamino derivative 39,234 which reacts with alcohols, ethanethiol and various amino compounds, such as hydrazines and guanidine, by replacement of the methyl(nitroso)amino group.235 Reaction with aziridine affords the aziridinyl compound 40f or the 2-(aziridin-l-yl)ethylainino derivative 40g, depending on the conditions. 

The presence of a 5-oxo group in the 1,2,4-triazines, as in 3-hydrazino-2,5-dihydro-5-oxo[l,2,4]triazines, does not alter the direction of cycliza-tion by the action of nitrous acid. The initial products are azido compounds 1016, which can cyclize spontaneously to tetrazolo[l,5-b][l,2,4]triazines 1017 (77JHC1221, 77JOC1866) rather than the previously reported isomeric structure. On the other hand, when the cyclization onto N-2 is impossible, as in derivative 1018, the azidotetrazolo equilibrium 1018 1019 exists (76JOC2860 77JOC1866). It exists in the solid state at least as the tetrazole derivative (Scheme 190). 

The studies of Bunton et al (Ref 38) using heavy oxygen (18Q) are particularly noteworthy in elucidating the self-ionization process. With moderately dilute nitric acid they found that nitrations required presence of nitrous acid. Ingold and co-workers (Ref 36c) suggest that the action of nitrous acid is as follows ... 

As already mentioned, Bunton and Halevi (Ref 38) found that ca 60% nitric acid requires the presence of nitrous acid for it to be a nitrating agent. Ingold et al (Ref 36c) postulated the action of nitrous acid to proceed via reactions 9, 10 11. Now in competition with reaction 11, there may be a nitrosation reaction ... 

Isolated salts of nitrolic acids , produced by action of nitrous acid on 1-nitroalka-nes, are explosive. 

The reaction of Curtius, which is especially to be preferred in the case of the higher members on account of the favourable solubilities of the intermediate products, involves as its first stage the preparation of the hydrazide from an ester (or acid chloride). The hydrazide is then converted, usually very readily, by the action of nitrous acid into the azide. In many cases it is more convenient to prepare the azide by treating an acid chloride with sodium azide previously activated with hydrazine hydrate.1 Azides easily undergo thermal decomposition, the two azo nitrogen atoms being eliminated as elementary nitrogen. In this way, however, the same radicle is formed as was invoked above to explain the Hofmann reaction ... 

The practical effect of the condensation consists, therefore, in the conversion of methylene into > C=0. The same result is attained in a quite similar reaction by the action of nitrous acid on ketones (cf. the synthesis of diacetyl from methylethyl ketone). 

Nitroso-/3-naphthol has been made by the action of hydroxyl-amine hydrochloride on /3-naphtho-quinonc-chlorimide 1 by the action of sulfuric acid upon a solution of potassium or sodium nitrite and the sodium salt of /3-naphthol 2 by the action of sodium nitrite upon an alcoholic solution of zinc chloride and /3-naphthol 3 by the action of sodium nitrite upon /3-naphthol suspended in zinc sulfate solution 4 by the action of nitrous acid on /3-dinaphthol methane 6 and by the action of nitrosyl sulfate upon the sodium salt of /3-naphthol.6... 

Benzotriazole has been prepared directly by the action of nitrous acid on 0-phenylenediamine1 and by the hydrolysis of an acylated or aroylated benzotriazole which has been previously prepared by the action of nitrous acid on the corresponding mono acylated or aroylated 0-phenylenediamine.2 3 4-i The above procedure is the direct method and gives better over-all yields than the methods involving several intermediate steps. Most methods described in the literature employ mineral acid. Acetic acid is much more satisfactory. 

Cyclooctanone has been prepared by distilling the calcium and thorium salts of azelaic acid, by heating azelaic acid with barium oxide in the presence of iron, by the action of nitrous acid on l-(aminomethyl)-cycloheptanol, by Dieckman cyclization of azelaic acid dimethyl ester and diethyl ester, and by ring expansion of cycloheptanone with diazomethane. ... 

General methods for the preparation of /raws-stilbenes have been covered previously. 4,4 -Dimethoxystilbene has been prepared from deoxyanisoin and -propylmagnesium iodide, by treatment of thiophenol with 2-bromo-l,l-di-/>-methoxyphenyl-ethane, and by the action of nitrous acid on the corresponding... 

By the action of nitrous acid in hydrochloric acid solution on bromo-phenylcystine, prepared by Baumann s method, chlorobromophenyl-thiopropionic acid was obtained, which, on reduction, gave bromophenyl-thiolactic acid. This was identical with the substance prepared from j8-iodopropionic acid and sodium bromophenylmercaptan —... 

Its composition, C H7N04, was established in 1833 by Boutron-Charlard and Pelouze, and confirmed by Liebig. In 1848 Piria showed that aspartic acid was converted into malic acid by the action of nitrous acid, and he regarded aspartic acid and asparagine as the two amides of malic acid... 

This assumption of Pauly s was confirmed by Knoop and Windaus, who found that histidine is resistant to reduction by sodium and alcohol whereas the pyrimidine rii is very unstable towards this reagent. On reducing Frankel s oxydesaminohistidine, which is obtained from histidine by the action of nitrous acid, they obtained /8-imidazole-propionic acid. This compound was identical with the synthetical product prepared from glyoxylpropionic acid, ammonia and formaldehyde — ... 

No Walden inversion was found to take place when amino acids were converted into the corresponding hydroxy acid by the action of nitrous acid. It was therefore possible to determine the relationship of serine to glyceric acid d-serine was converted by nitrous acid into a glyceric acid which Neubei and Silbermann regarded as 1-glyceric acid on account of its relationship to 1-tartaric acid, but which Neuberg, a little later, stated required confirmation. 

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