Nitrosophenol salts

Nitrosophenols are formed very easily by the action of nitrous acid on phenols. Some salts of heavy metals have weak initiating properties. These are lead dini-trosophenate and lead trinitrosophloroglucinate. 

Due to the readiness with which it ignites under the direct influence of flame, lead dinitrosophenate has found a certain application in the manufacture of cap compositions for ignition by spark or flame. Its disadvantage lies in its relatively low stability heating to 120°C causes explosion after 2 hr, and after 10 days of heating at 80°C marked decomposition occurs. 

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It can act either as a nitrosophenol or as a quinone monoxime. Coloured derivatives, e.g. the sodium salt, are derived from the quinone form. Direct methylation gives a coloured compound which has been shown to be quino-nemethoxime OlCeH4tNOCH3 p-nitrosoani-sole CH30 C6H4 N0 has been obtained by another route and is colourless. 

In reactions of A,A-dimethylaniline, care must be taken in the final isolation of the free p-nitrosoamine from its salt, since prolonged treatment with excessive alkali leads to the formation of p-nitrosophenol [21a]. By the way, the initial proof that the product of nitrosation is the para isomer was simply based on the observation that, after prolonged add hydrolysis of p-nitrosophenol, a product formed which had an odor that resembled that of 1,4-benzoquinone. It is to be hoped that more substantial structure proofs are used today. 

The nitrosation of phenols proceeds in a manner similar to that of tertiary amines. For example, l-nitroso-2-naphthol has been prepared from the sodium salt of /9-naphthol by treatment with sodium nitrite and sulfuric acid near 0°C [29], This general procedure, suitably modified, has been used to prepare other nitrosophenols such as p-nitrosophenol (m.p. 135°-136°C) [30]. 

At low acid concentrations, nitric oxide tends to form. This evidently may attack nitrosophenol to form diazonium compounds directly. The diazonium salts, in turn, may couple with unreacted phenol to give colored products. Nitrous acid may also produce nitrophenols from phenols. The mechanism of this reaction may involve oxidation of initially formed nitrosophenols, homolytic attack by nitrogen dioxide, or nucleophilic attack by nitrite ions [1]. 

The Baudisch reaction295 makes it possible simultaneously to introduce a nitroso and a hydroxyl group in the ortho-position to one another. In this reaction NOH radicals are produced by oxidation of hydroxylamine or reduction of nitrous acid these radicals, in conjunction with an oxidizing agent and in the presence of a copper salt as catalyst attack the aromatic nucleus. Yields are seldom very high, but few o-nitrosophenols are easily prepared in other ways. Cronheim296 has reported the first preparation of fifty mono-and di-substituted n-nitrosophenols by the Baudisch reaction. 

Certain nitroso phenols and polyhydroxy compounds are exceptions where the exchange takes place under relatively mild conditions and sometimes without the need for a catalyst. For example,/7-nitrosophenol and ammonium salts, when heated on a steam-bath for 0.5 hour, give 50% of /7-nitrosoaniline, 1049.cf.1050 and l-nitroso-2-naphthol and aqueous methylamine solution at 35° give 90% of iV,iV-dimethyl-1 -nitroso-2-naphthylamine.1051 The easier reaction s due to the tautomerism of these phenols with the ketonic isomers, e.g.9 for nitrosophenol ... 

Nitration of p-cymene by fuming nitric add leads to 2,4-dinitrotoluene.1184 Heating 1,6-dihydro-l-methyl-6-oxonicotinic acid with nitric acid (d 1.52) under reflux gives 1-methyl-3,5-dinitro-2(li/)-pyridone in good yield.1185 2,6-Dibromo-4-nitrosophenol is formed quantitatively from 3,5-dibromo-4-hydroxybenzoic acid and sodium nitrite in aqueous alcohol.166,1183 Nitrous acid replaces hydroxymethyl groups in phenols by nitro groups,1186 and diazonium salts replace them by diazo groups.1187... 

An example of p-nitrosophenolate anion is very spectacular indeed. In various salts this anion is differently hydrated and this is a cause of variation of the ring geometry and consequently of the energy content of the ring. Figure 6 shows the relevant data for p-nitrosophenolates of sodium (trihydrate) [29], magnesium (hexahydrate) [30], and lithium (dihydrate) [31]. 

The salt so formed crystallizes in yellow needles. The free amine, which is liberated from its salts by bases, crystallizes in green plates, which melt at 85°. When p-nitrosodimethyl-aniline is boiled with an alkali, dimethylamine and a salt of nitrosophenol are formed —... 

Other slyphnates Lead dinitroresorcinatc Nitrosophenol sails Nitraminc salts Salts of mctazonic acid Salts of oxalic acid Peroxides... 

A total of 4 mL 30% hydrogen peroxide was added to a solution of 1 g phenol, 4 g hydroxylamine hydrochloride, and 2 g sodium pentacyanoaminneferrate(II) in 200 mL water and 60 mL petroleum ether (b.p. 30-70°C). The mixture was stirred at room temperature for 1 h, the ether layer was separated, and the aqueous layer was extracted with petroleum ether repeatedly until the green color was scarcely found in the ether layer. The petroleum ether extracts of o-nitrosophenol were transferred to a flask, which was connected to an empty flask by means of a T-tube fitted with a glass stopcock. After air was pumped out through the stopcock, the empty flask was cooled with an ice-salt mixture, and the flask containing the extract was warmed with hot water. o-Nitrosophenol, which was volatilized with the petroleum ether, was condensed in the ice-cooled flask. 

Synthesis of o-nitrosophenols from benzene or substituted benzenes, hydroxylamine and hydrogen peroxide in the presence of copper salts ... 

Nitroso-con unds. (a) C-Nitroso-compoimds. These are generally found as nitrosophenols or p-nitroso-derivatives of dialkylanilines. Their colour is usually green (p-nitrosodialkylani-lines) or yellow (salts of p-nitrosodiaUcylanilines, nitrosophenols). 

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