Compounds nitroso

Simple alkyl nitroso compounds are unstable under normal conditions and 

Isomerization of nitroso compounds to the corresponding oxime is rapid at temperatures above the melting point of the dimer or in the presence of metallic or other reactive surfaces or in certain non-aqueous solvents . For the nitroso-methane-formaldoxime isomerization the activation energy was estimated as 30-40 kcal.mole . The thermal gas-phase isomerization of nitrosomethane, reaction (1), has been studied by a flow technique at low pressures, and found to be highly sensitive to reaction conditions, especially to the nature and extent of the surfaces. Under conditions favourable to the homogeneous gas phase process, 27.1 kcal.mole and log /l(sec ) = 8.9. The low pre-exponential factor was interpreted in terms of a cyclic transition state, viz. 

The rate of decay of nitrosomethane (formed in the photolysis of azomethane-nitric oxide mixtures at 25° C) to form the stable dimer, reaction (2), was measured by infrared techniques and the homogeneous second order rate coefficient = 87 l.mole. sec was derived. The cis and trans iomers of nitrosomethane have been characterized and the experimental conditions which favour the formation of each of the dimers and the rearrangement to formaldoxime have been described  

The thermolysis of 2-methyl-2-nitrosopropane has been briefly examined. Isomerization to the oxime is structurally impossible and it appears that the decomposition occurs predominantly via C-N cleavage 

The thermal cis-trans isomerizations of nitrosomethane and 2-methyl-l-nitroso-propane obey first order kinetics with activation energies (kcal.mole ) and log y4(sec ) of 19.1 and 22.1, and 11.6 and 13.9, respectively . Both direct and indirect isomerization mechanisms were considered, viz. 

The reduction of nitroso compounds has been used for the synthesis of aminodiphenyl-amines601 601 substituted /t-phenylenediamines 603), and aminophenols 604) on the laboratory scale  

The reduction of nitroso compounds in the presence of ketones can be used for the reductive alkylation of amines  

N-oxides can be converted electrochemically into the corresponding amines. One of the uses of the reaction is for the synthesis of bactericides. 

Structural studies have been made of the free radical [(CH3)3C] 2NO (N—0, 1-28 A), of nitrosomethane, CH3NO, (CNO, 113° assuming N-0, 1-22 A), and of p3CNO, in which N-0 is 1-17 A and angle CNO 121°. The C-N bond is abnormally long (1-55 A) as in the nitro compounds, CF3NO2, etc. (p. 659). Many 

5% Pd-C.198 A high yield of o-hydrazotoluene was obtained by hydrogenation over 5% Pd-C in a two-phase solution containing alcohol/THF and aqueous sodium hydroxide in the presence of 2,3-dichloro-1,4-naphthoquinone (eq. 9.70). 

Primary and secondary aliphatic nitroso compounds, with an a-hydrogen, are unstable and readily rearrange to or exist as the more stable tautomeric oximes. Therefore, these nitroso compounds can be understood to be hydrogenated in the form of the oximes. On the other hand, tertiary and aromatic nitroso compounds as well as (V-nitrosamines may be hydrogenated as the compounds with a true nitroso group. 

Aromatic nitroso compounds are, like aromatic nitro compounds, hydrogenated rapidly to the amines over palladium catalysts,200,201 as seen in an example shown in eq. 9.71. However, in contrast to the cases with aromatic nitro compounds, a kinetic 

N-Nitrosamines. Hydrogenation of IV-nitrosamines over palladium, platinum, and nickel catalysts usually proceeds to give amines, and in rather few cases have unsym-hydrazines been obtained in good yields. Amines may also be formed directly from nitrosamines by a rather complex parallel reaction. 

The presence of ferrous salts or ferrous salts with hydroxide ion was also claimed to improve the yields of hydrazines. The shortest reaction time and largest conversion to W/V-di methyl hydrazine was obtained in the presence of 0.5 mmol of ferrous sulfate in the hydrogenation of 15 ml of A-nilrosodi methyl amine over 1 g 5% Pd-C in 135 ml of water at 45°C and 0.28-0.34 MPa H2.212 Under similar conditions, 5% Pd-C containing 5 mmol of sodium hydroxide and 1 mmol of ferrous sulfate per gram of catalyst gave 50% reaction in 57 min, 98.9% N,N-di-methylhydrazine, and a ratio of 41 moles of the hydrazine per mole of amine.213 

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N-Nitrosodiethylamine. Add 36-5 g. (51-5 ml.) of diethylamine slowly to the calculated quantity of carefully standardised 5A-hydra chloric acid cooled in ice (1). Introduce the solution of the hydi ochloride into a solution of 39 g. of sodium nitrite (assumed to be of 90 per cent, purity) in 45 ml. of water contained in a 250 ml. distilling flask. Distil the mixture rapidly to dryness. Separate the yellow upper layer of the nitrosamine from the distillate saturate the aqueous layer with soUd potassium carbonate and remove the nitroso compound which separates and add it to the main product. Dry over anhydrous potassium carbonate and distil. Collect the diethylnitrosamine at 172-173-5°, The yield is 41 g. 

Secondary and tertiary amines are not generally prepared in the laboratory. On the technical scale methylaniline is prepared by heating a mixture of aniline hydrochloride (55 parts) and methyl alcohol (16 parts) at 120° in an autoclave. For dimethylaniline, aniline and methyl alcohol are mixed in the proportion of 80 78, 8 parts of concentrated sulphuric acid are added and the mixture heated in an autoclave at 230-235° and a pressure of 25-30 atmospheres. Ethyl- and diethyl-anihne are prepared similarly. One method of isolating pure methyl- or ethyl-aniline from the commercial product consists in converting it into the Y-nitroso derivative with nitrous acid, followed by reduction of the nitroso compound with tin and hydrochloric acid ... 

The nitroso compound (diphenyinitrosamine) of the purely aromatic secondary amine diphenylamine is a crystalline solid, and therefore provides an interesting preparation eminently suitable for students ... 

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

The p-nitroso compounds do not give Liebermann s nitroso reaction. 

Some reference to the use of nitrous acid merits mention here. Primary aromatic amines yield diazonium compounds, which may be coupled with phenols to yield highly-coloured azo dyes (see Section IV,100,(iii)). Secondary aromatic amines afford nitroso compounds, which give Liebermann a nitroso reaction Section IV,100,(v). Tertiary aromatic amines, of the type of dimethylaniline, yield p-nitroso derivatives see Section IV,100,(vii). ... 

Benzene and some of its derivatives react with solutions of mercuric nitrate in concentrated nitric acid to give nitrophenols. These reactions, known as oxynitrations may proceed by mercuration followed by nitroso-demercuration the resulting nitroso compound becomes a diazonium compound and then a phenol, which is nitrated. ... 

Treatment of 2-(arylamino)selenazoles with sodium nitrite in glacial acetic acid at room temperature gives the corresponding nitroso compounds instantaneously (Scheme 381 (29). These compounds give rise to... 

A Alkylarylammes resemble secondary alkylammes m that they form A nitroso compounds on reaction with nitrous acid... 

Reactions with Organic Compounds. Tetrafluoroethylene and OF2 react spontaneously to form C2F and COF2. Ethylene and OF2 may react explosively, but under controlled conditions monofluoroethane and 1,2-difluoroethane can be recovered (33). Benzene is oxidized to quinone and hydroquinone by OF2. Methanol and ethanol are oxidized at room temperature (4). Organic amines are extensively degraded by OF2 at room temperature, but primary aHphatic amines in a fluorocarbon solvent at —42°C are smoothly oxidized to the corresponding nitroso compounds (34). 

By the nitrosation of 2-naphthalenol and the reaction of the nitroso compound with sodium bisulfite. By nitrosation/reduction of 6-hydroxy-2-naphthalenesulfonic acid. 

The effects of uv radiation on V/-nitroso compounds depend on the pH and the medium. Under neutral conditions and ia the absence of radical scavengers, these compounds often appear chemically stable, although the E—Z equiUbrium, with respect to rotation around the N—N bond, can be affected (70). This apparent stabiUty is due to rapid recombination of aminyl radicals and nitric oxide [10102-43-9] formed duting photolysis. In the presence of radical scavengers nitrosamines decay rapidly (71). At lower pH, a variety of photoproducts are formed, including compounds attributed to photoelimination, photoreduction, and photo-oxidation (69). Low concentrations of most nitrosamines, even at neutral pH, can be eliminated by prolonged kradiation at 366 nm. This technique is used ki the identification of /V-nitrosamines that are present ki low concentrations ki complex mixtures (72). 

BD rat represents a particular strain used to test carcinogenicity of some V/-nitroso compounds. Refs. 7 and 62. 

There is insufficient evidence to unequivocally link nitrosamine exposure to elevated risk for human cancer (159). There are, however, a number of specific cases, especially with respect to the tobacco-related nitrosamines, in which exposure to V/-nitroso compounds is of concern. The strongest evidence in this context is probably that relating to oral cancer rates among habitual users of smokeless tobacco (snuff). Oral cancer rates among this group are significantly elevated over those of nonusers, and /V-nitrosonornicotine, and 4-(methylnitrosamino)-l-(3-pyridinyl)-l-butanone [64091 -91 both of... 

I. K. O Neill, J. Chen, and H. Bartsch, eds.. Relevance to Human Cancer of N-Nitroso Compounds, Tobacco Smoke andMjcotoxins, lARC Scientific Pubhcation No. 105, International Agency for Research on Cancer, Lyon, Prance, 1991. 

R. A. Scanlan and S. R. Tannenbaum, eds., N-Nitroso Compounds, American Chemical Society, Washington, D.C., 1981. 

W. Lijinsky, Chemist and Biology of N-Nitroso Compounds, Cambridge University Press, Cambridge, U.K., 1992. 

M. C. Archer, S. R. Tannenbaum, andj. S. Wishnok, in E. A. Walker, P. Bogovski, and L. Gticiute, eds.. Environmental N-Nitroso Compounds Mnaljsis andEormation, lARC Scientific PubHcation No. 14, Lyon, France, 1976, pp. 141—145. 

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