Oxidation aniline

Aniline Oxidation. Even though this is quite an old process, it still has limited use to produce hydroquinone on a commercial scale. In the first step, aniline is oxidized by manganese dioxide in aqueous sulfuric acid. The resulting benzoquinone, isolated by vapor stripping, is reduced in a second step by either an aqueous acidic suspension of iron metal or by catalytic hydrogenation. 

Allyl or benzyl groups on the nitrogen facilitate the process. The rearrangement appears to be intramolecular (13), proceeding by a cycHc mechanism as in the case of /V-2-buteny1-/V-metby1 aniline oxide giving /V-methyl-0-1-methylallyl-/V-phenyl-hydroxylamine. 

The result of theoretical investigations have suggested that cleavage of a B—H bond occurs to initiate ammonia borane dehydrogenation [38]. Alternatively, the oxidative N—H addition of ammonia to the dehydrogenated intermediate C may constitute a feasible reaction pathway due, in particular, to the fact that ammonia and aniline oxidative addition to la and related iridium-PCP systems has been reported experimentally [39]. 

Analogous high-yield cyclizations were reported with l-amino-2-nitro-derivatives of pyridines and isoquinolines, which gave the corresponding furoxans [53,54], Anilines oxidized in the presence of indoles afforded Schiff s bases from 2- and/or 3-position in low yield [55], An unexpected rearrangement occurred on treatment of l-phenyl-4-methyl-5-aminopyrimidinone with DIB and catalytic amounts of nickel dichloride, resulting in the formation of an imidazole derivative [56] ... 

The (NH3)50s + fragment in equation (9) is a strong tt-donor because NH3 is strongly a-donor but not a r-acceptor ligand, and it prefers to bind to one C=C bond of aniline. Oxidation to Os causes a sharp fall-off in r-donor power because the extra positive charge stabilizes the d orbitals, and the complex rearranges to the N-bound aniline form. This illustrates how the electronic character of a metal can be... 

Fig. 6. An electrochemical reactor used for aniline oxidation on a lead dioxide packed-bed anode (A) lead anode (B) 1 mm lead pellets (C) stainless steel cathode (D) Na-fion 427 membrane (E) stainless steel retaining screen (F) glass beads (G) gasket (H) inlet (I) outlet (J) cathode gas vent. (Adapted from (27]).

Fuchsin, Magenta.—In 1859 Verguin in France found that crude aniline oxidized by means of stannic chloride yielded a red dye which was named fuchsin and also magenta. Other oxidizing agents were used later, e.g., mercuric chloride, arsenic acid, mono-nitro benzene. 

Manganese(ll) sulfate is formed as a byproduct in the oxidation of organic compounds with manganese(IV) oxide in the pre.sence of sulfuric acid, e.g. in the production of p-anisaldehyde. Aniline oxidation to p-benzoquinone is no longer industrially important in Western industrialized countries, so most MnSOg is produced from MnO or MnCOv... 

The finding reported in these papers36,37 is in fact inconsistent with the results of previously mentioned electrochemical studies, the authors of which have found that at least both the head-to-tail and tail-to-tail dimers are formed under very similar experimental conditions. Furthermore, the observation of only the reduced dimer (and, similarly, trimer) is rather intriguing, as it has been demonstrated many times that the dimers, being the products of the initial stages of aniline oxidation, are easier to oxidize than the parent compound. 

In general, 1,3-dipolar molecules such as azidoformate or ethyl diazoacetate do not undergo addition to cycloproparenes. yV-(Benzylidene)aniline //-oxide is an exception to this general rule, and formed a 6-membered benzoxazine 13 in 54% yield on reaction with benzocyclo-propene. ... 

Oxidation of anilines. Oxidation of anilines with this reagent gives azobenzenes (N—N coupling), quinonimines (N—C coupling), and phenazines. No products of C—C coupUng have been isolated. 

Hydroquinone 50.000 Aniline oxidation Phenol hydroxylation p-Di isopropyl benzene hydroperoxidation... 

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