Nitroso-benzene

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. ... 

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). 

V-Methyl-7V-nitroso-p-toluenesulfonamide (diazald) [80-11-5] M 214.2, m 62 . Crystd from benzene by addition of pet ether, store in a refrigerator. 

More surprising, in view of its poor electrophilic character, is that phcnylnitrene, generated by deoxygenation of nitroso benzene with triethyl phosphite in a mixture of benzene and 2,2,2-trifluoroethanol, yields 1-phenyl-1//-azepine (26), a rare example of a stable 1-aryl-lH-azepine.170... 

Nitroso-5//-dibenz[/>,/]azepine (9, R = NO) is relatively stable to photolysis under argon, whereas in benzene solution in the presence of oxygen, irradiation induces an oxidative Fischer -Hepp-type rearrangement to 2-nitro-5//-dibenz[6,/]azepinc (10, R = N02), accompanied by ring contraction to acridine-9-carbaldehyde184 (see also Section 3.2.2.4.). 

In triethylamine instead of benzene the reaction products are completely different, and are indicative of a homolytic process involving an initial electron transfer from triethylamine followed by a hydrogen atom transfer. Scheme 10-68 gives the major products, namely 1,3,5-tri-tert-butylbenzene (10.36, 20%), the oxime 10.39 (18%), formed from the nitroso compound 10.38, and the acetanilide 10.37 (40%). ESR and CIDNP data are consistent with Scheme 10-68. In their paper the authors discuss further products which were found in smaller yields. 

There is no reference to the formation of the ortho nitroso amine in the benzene series, indeed the formation and characterisation of ortho nitroso amines from any reaction has only been reported once or twice79. When the para position is blocked by a substituent, de-nitrosation so the secondary amine can occur80 a certain amount (which depends on the conditions) of denitrosation occurs also, concurrently with the rearrangement81, so that N-nitroso-N-methylaniline (XLVII) yields N-methylaniline (XLVIII) as well as the rearrangement product p-nitroso-N-methylaniline XLIX, viz. 

Note There is considerale variety in this category, including, for example, the use of hydroxyimino- or nitroso derivatives of benzene as substrates. 

Allyl (27, 60, 119-125) and benzyl (26, 27, 60, 121, 125-133) radicals have been studied intensively. Other theoretical studies have concerned pentadienyl (60,124), triphenylmethyl-type radicals (27), odd polyenes and odd a,w-diphenylpolyenes (60), radicals of the benzyl and phenalenyl types (60), cyclohexadienyl and a-hydronaphthyl (134), radical ions of nonalternant hydrocarbons (11, 135), radical anions derived from nitroso- and nitrobenzene, benzonitrile, and four polycyanobenzenes (10), anilino and phenoxyl radicals (130), tetramethyl-p-phenylenediamine radical cation (56), tetracyanoquinodi-methane radical anion (62), perfluoro-2,l,3-benzoselenadiazole radical anion (136), 0-protonated neutral aromatic ketyl radicals (137), benzene cation (138), benzene anion (139-141), paracyclophane radical anion (141), sulfur-containing conjugated radicals (142), nitrogen-containing violenes (143), and p-semi-quinones (17, 144, 145). Some representative results are presented in Figure 12. 

Photolysis of n-octylnitrite in solvents that are poor hydrogen donors (e.g., benzene) results primarily in the formation of the dimer of 4-nitroso-l-octanol. 

The procedure described for the preparation of l-(m-nitro-phenyl)-3,3-dimethyltriazene is the method of Elks and Hey,2 and the preparation of m-nitrobiphenyl is also a modification of their procedure. The other principal methods for the preparation of m-nitrobiphenyl are the decomposition of N-nitroso-w-nitroacetanilide in benzene 3 and the decomposition of alkaline m-nitrobenzenediazohydroxide in benzene.4 Other methods that have been reported include the decomposition of potassium ire-nitrobenzenediazotate in benzene with acetyl chloride,6 the decomposition of m-nitrobenzoyl peroxide in boiling benzene,6 the decomposition of benzenediazonium borofluoride in nitrobenzene 7 at 70°, and the reduction of 4-(3 -nitrophenyl)-benzenediazonium acid sulfate in boiling ethanol.8... 

The problem of retention of asymmetry of the formed free radical in the fast geminate recombination of radicals was studied by photolysis of the optically active azo-compound PhMeCH—N=NCH2Ph [88,89]. The radical pair of two alkyl radicals was initiated by the photolysis of the azo-compound in benzene in the presence of 2-nitroso-2-methylpropane as a free radical acceptor. The yield of the radical pair combination product was found to be 28%. This product PhMeEtCCH2Ph was found to be composed of 31% 5,5 -(-)(double retention), 48% meso (one inversion), and 21% R.R(+) double inversion. These results were interpreted in terms of the competition between recombination (kc), diffusion (kD), and rotation (kml) of one of the optically active radicals with respect to another. The analysis of these data gave kxo[Pg.126]

Several procedures were developed for the transformation (223—>-224). The most commonly used procedures are based on treatment of the nitroso acetal with benzene saturated with HC1 (204, 205) and by the addition of a catalytic amount of para -toluenesulfonic acid or trifluoroacetic acid (206). The introduction of branched radicals at the silicon atom decelerates elimination of silanol. 

The nitroso-group in the p-position has a remarkable influence in making possible the hydrolytic removal of the dimethylamino group from the benzene ring. The reaction is used technically for the preparation of secondary amines. (Trimethylamine is obtained by heating ammonium chloride with formaldehyde.)... 

A very early indication that C-nitroso-compounds are particularly susceptible to radical attack was the methyl affinity value of 105 determined for nitrosobenzene (Heilman el al., 1957). This figure reflects the reactivity of nitrosobenzene, relative to that of benzene, towards attack by methyl radicals. It was apparently several years before this reactivity was linked with nitroxide formation... 

The PE spectrum of nitrosobenzene has been investigated by Rabalais and Colton129 and by Green and coworkers128. Unfortunately, the published IP values are considerably at variance. From the characteristic IPs of C-nitroso compounds only IP(n ) = 8.51 eV could be assigned as the first IP. IP2 and IP3 were identified as ionizations of electrons from the benzene MOs ni and 7r3 (Table 13). 

The H-NMR spectra of amino, nitro and nitroso compounds have been reviewed16,17, and the effects of these substituents on the proton chemical shifts have been investigated16. Table 4 gives these substituent effects for mono-substituted benzenes. 

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