Nitrosobenzene

Add 4 4 g. of recrystaUised -phenylhydroxylamine to a mixture of 20 ml. of concentrated sulphuric acid and 60 g. of ice contained in a 1 litre beaker cooled in a freezing mixture. Dilute the solution with 400 ml. of water, and boil until a sample, tested with dichromate solution, gives the smell of quinone and not of nitrosobenzene or nitrobenzene (ca. 10-15 minutes). Neutralise the cold reaction mixture with sodium bicarbonate, saturate with salt, extract twice with ether, and dry the ethereal extract with anhydrous magnesium or sodium sulphate. Distil off the ether p-aminophenol, m.p. 186°, remains. The yield is 4-3 g. 

In a 2 litre bolt-head flask, equipped with an efficient mechanical stirrer, place 60-5 g. (50 ml.) of pure nitrobenzene and a solution of 30 g. of ammonium chloride in 1 litre of water. Stir vigorously and add 75 g. of a good quality zinc powder (about 90 per cent, purity) in small portions over a period of 5 minutes. The main reaction occurs about 5 minutes after the addition and the temperature rises. When the temperature reaches about 65°, add enough ice to the weU-stirred mixture to reduce the temperature to 50-55°. Filter the solution through a Buchner funnel twenty minutes after the first portion of zinc powder was introduced wash the zinc oxide residues with 600-700 ml. of boiling water. 

10-15 minutes). Neutralise the cold reaction mixture with sodium bicarbonate, saturate with salt, extract twice with ether, and dry the ethereal extract with anhydrous magnesium or sodium sulphate. Distil off the ether p-aminophenol, m.p. 186°, remains. The yield is 4-3 g. 

Substances of this kind are called nitrones Their method of formation is quite analogous to that of the oximes from aldehydes and hydroxylamine. 

These nitrones are identical with the N-ethers of the aldoximes and are also formed—when an alkyl group occupies the place of C6H6—by the action of alkyl halides on the stereoisomeric /3-aldoximes  

The nitrone from phenylhydroxylamine and benzaldehyde can easily be prepared in beautiful crystals from alcoholic solutions of these components. 

Finally, it is interesting to note that the reduction of nitroethylene, an olefinic nitro-compound having a structure analogous to that of nitrobenzene, leads to acetaldoxime. 

Phenylnitroethylene, which is much more easily obtained (see p. 160), reacts in an analogous manner, yielding phenylacetaldoxime C6H8.CH2.C=NOH (Bouveault). In any case both these nitroethy-H 

Submitted by George H. Coleman, Chester M. McCloskey, and Frank A. Stuart. 

To this cold solution or suspension of /3-phenylhydroxylamine, a cold solution of sulfuric acid (750 ml. of concentrated acid and sufficient ice to bring the temperature down to —5°) is added with stirring. An ice-cold solution of 170 g. of sodium dichromate dihydrate in 500-750 ml. of water is added as rapidly as it can be poured into the mixture, which is stirred or swirled (Note 8). After 2 to 3 minutes, the straw-colored precipitate of nitrosoben-zene is collected on a Buchner funnel and washed with 1 1. of water (Note 9). 

The crude nitrosobenzene is steam-distilled (Note 10), and the distillate is collected in a receiver cooled by ice (Note 11). The nitrosobenzene is finely ground in a mortar, transferred to a Buchner funnel, and washed with water until the washings are no longer brown. After it has been sucked as dry as possible on the filter the nitrosobenzene is pressed between layers of filter paper (or other porous paper). One or two changes of paper may be necessary. The yield of nitrosobenzene melting at 64-67° is 128-138 g. (49-53%) (Notes 12 and 13). If a purer product is desired, the crude nitrosobenzene can be recrystallized from a small amount of alcohol with good cooling, and the product dried over calcium chloride at atmospheric pressure. 

Contact with nitrobenzene, phenylhydroxylamine, and nitrosobenzene or prolonged breathing of the vapors should be avoided. 

Vigorous stirring is necessary in order to prevent the zinc dust from caking on the bottom of the crock. The submitters employed two mechanically driven stirrers in order to keep the zinc dust in suspension. The checkers used a single paddle stirrer successfully. 

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By condensing nitroso derivatives with primary amines. Nitrosobenzene and aniline, for example, readily give azobenzene. This method is seldom used... 

The initial product, nitrosobenzene, is so easily reduced to p-phenylhydroxyl-amine that it has never been isolated in the free state, but its presence has been established by reaction in solution with hydroxylamine to 3deld a phenyldi-azonium salt, which couples readily with a a-naphthylamine to form the dyestuff phenyl-azo-a-naphthylamine (compare Section IV,77) ... 

Under the cataljdic influence of alkali, nitrosobenzene and p-phenylhydroxyl-amine react to yield azoxybenzene ... 

Nitrosobenzene may be obtained by the oxidation of P pheiiylhydroxylamine with acid dichromate solution at 0° ... 

The reduction of the nitro group to yield aniline is the most commercially important reaction of nitrobenzene. Usually the reaction is carried out by the catalytic hydrogenation of nitrobenzene, either in the gas phase or in solution, or by using iron borings and dilute hydrochloric acid (the Bechamp process). Depending on the conditions, the reduction of nitrobenzene can lead to a variety of products. The series of reduction products is shown in Figure 1 (see Amines byreduction). Nitrosobenzene, /V-pbenylbydroxylamine, and aniline are primary reduction products. Azoxybenzene is formed by the condensation of nitrosobenzene and /V-pbenylbydroxylamine in alkaline solutions, and azoxybenzene can be reduced to form azobenzene and hydrazobenzene. The reduction products of nitrobenzene under various conditions ate given in Table 2. 

Fig. 1. Reduction products of nitrobenzene (1) nitrosobenzene [98-95-3] (2) /V-pbenylbydroxyl amine [100-65-2] (3) aniline [62-53-3] (4) azoxybenzene...

Oxidation. Aromatic amines can undergo a variety of oxidation reactions, depending on the oxidizing agent and the reaction conditions. For example, oxidation of aniline can lead to formation of phenyUiydroxylamine, nitrosobenzene, nitrobenzene, azobenzene, azoxybenzene or -benzoquinone. Oxidation was of great importance in the early stages of the development of aniline and the manufacture of synthetic dyes, such as aniline black and Perkin s mauve. 

Primary synthesis of arylazopyrimidines is used (52JCS3448). It is exemplified in the condensation of phenylazomalondiamidine with diethyl oxalate to give the azopyrimidine (833) (66JCS(C)226). Finally, 5-phenylazopyrimidine may be made by the condensation of pyrimidin-5-amine with nitrosobenzene (5UCS1565) but the reaction seems to have been overlooked for many years. 

Phenazine mono-N-oxides have also been prepared from nitrobenzene derivatives. Condensation of nitrobenzene with aniline using dry NaOH at 120-130 °C results in modest yields of phenazine 5-oxide, although the precise mechanism of this reaction is not well understood (57HC(ll)l) with unsymmetrical substrates it is not possible to predict which of the isomeric fV-oxides will be produced. Nitrosobenzene derivatives also function as a source of phenazine mono-fV-oxides thus, if 4-chloronitrosobenzene is treated with sulfuric acid in acetic acid at 20 °C the fV-oxide is formed (Scheme 21). 

The replacement of rhodium from a wide range of rhodacycles to form condensed furans, thiophenes, selenophenes, tellurophenes and pyrroles has been widely explored and a range of examples is shown in Scheme 97. The rhodacycles are readily generated from the appropriate dialkyne and tris(triphenylphosphine)rhodium chloride. Replacement of the rhodium by sulfur, selenium or tellurium is effected by direct treatment with the element, replacement by oxygen using m-chloroperbenzoic acid and by nitrogen using nitrosobenzene. 

Cyclopropenones react with nitrosobenzene by an O-initiated attack at C-1 to produce isoxazolin-5-ones (75TL3283, 78USP4053481), and an isoxazolin-5-one was produced as a by-product in the photolysis of nitroethylene (78AJCU3). Substituted oxazolin-5-ones have... 

Isoxazolin-5-imines were produced by nitrile oxide addition to cyanoacetates (62HC(17)l,p.7), by the reaction of nitrones with phenylacetonitrile (74CB13), and by base addition of nitrosobenzene to nitriles (Scheme 148) (72LA(762)154). 

Azetidine N-oxides produce isoxazolidines by a thermal ring expansion (77AHC(21)207, 75GEP2365391), and nitrosobenzenes react with alkenes to provide isoxazolidines (77AHC(21)207, 79IZV1059). 

IH-Azepine, 1-methoxy carbonyl-cycloaddition reactions, 7, 522 with nitrosobenzene, 7, 520 tricarbonyliron complex acylation, 7, 512-513 conformation, 7, 494 tricarbonylruthenium complex cycloaddition reactions, 7, 520 1 H-Azepine, l-methoxycarbonyl-6,7-dihydro-synthesis, 7, 507... 

Nitrosobenzene [586-96-9] M 107.1, m 67.5-68 , b 57-59 /18mm. Steam distd, then cryst from a small volume of EtOH with cooling below 0°, dried over CaCl2 in a dessicator at atm pressure, and stored under N2 at 0°. Alternatively it can be distd onto a cold finger cooled with brine at —10 in a vac at 17mm (water pump), while heating in a water bath at 65-70° [Robertson and Vaughan J Chem Educ 27 605 1950]. 

Other mild oxidising agents which abstract the terminal hydrogen atoms and thus facilitate disulphide formation may be used as vulcanising agents. They include benzoyl peroxide, p-nitrosobenzene and p-quinone dioxime. 

Nitroso-bakterien, n.pl. nitrosobacteria. -benzol, n. nitrosobenzene. -blau, n. nitroso blue, -gruppe, /. nitroso group, -kobaltwasser-stoffsaure, /. cobaltinitrous acid, -sulfo-saure, /. nitrososulfonic acid, -verbindung, /. nitroso compound. 

The nitroso group, — N = Op is one of the few nonhalogens that is an ortho- and para-directing deactivator. Explain by drawing resonance structures of the carbocation intermediates in ortho, mela, and para electrophilic reaction on nitrosobenzene, C<3Hs N = 0. 

Cleavage of the heterocycle is observed when oxepin reacts with l-chloro-4-nitrosobenzene to give 4-chloro-AL(6-oxohexa-2,4-dienylidene)aniline iV-oxide (6) in 62% yield.215... 

Whereas the production of arylnitrenes by the deoxygenation of nitrosobenzenes or nitro-benzenes by trivalent phosphorus reagents and their subsequent intramolecular ring expansion to 3//-azepines are well-known processes, the corresponding intermolecular reactions to form 1//-azepines have been exploited only on rare occasions and appear to be of little preparative value. For example, the highly electrophilic pentafluorophenylnitrene, obtained by deoxygenation of pentafluoronitrosobenzene with triethyl phosphite in benzene solution, produced a low yield (2-10%) of l-(pentafluorophenyl)-l//-azepine, which was isolated as its [4 + 2] cycloadduct with ethenetetracarbonitrile.169 With anisole as the substrate l-(pentafluorophenyl)-l//-azepin-2(3//)-one (16% bp 128 —130 C/0.4 Torr) was obtained. 

Generation of phenylnitrcne by thermal decomposition of phenyl azide in the same solvent mixture, or by deoxygenation of nitrosobenzene with triethyl phosphite in the absence of the trifluoroethanol, fails to yield the 1//-azepine. The role of the alcohol in promoting l//-azepine formation is not understood. 

Nitrosobenzene undergoes deoxygenation with triphenyl- or tributylphosphane in refluxing diethyl ether in the presence of an alkylamine to yield /V,A -dialkyl-3//-azepin-2-amines... 

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