Sulfuric acid, aniline oxidation

Quinoline from aniline, glycerol, sulfuric acid and oxidizing agent (e.g. PhN02). 

The most common reagent for nitration of benzene, simple alkylbenzenes and other less reactive compounds is a mixture of concentrated nitric and sulfuric acids. However, nitration of activated substrates, such as aniline, phenol or pyrrole, occurs with nitric acid alone or in water, acetic acid or acetic anhydride. Concentrated sulfuric acid can oxidize these substrates. A description of the use of other nitrating reagents is outside of the scope of this review, but can be found in Smith and March s Advanced Organic Chemistry29 or Larock s Comprehensive Organic Transformations30. 

Polyaniline (PANI) can be formed by electrochemical oxidation of aniline in aqueous acid, or by polymerization of aniline using an aqueous solution of ammonium thiosulfate and hydrochloric acid. This polymer is finding increasing use as a "transparent electrode" in semiconducting devices. To improve processibiHty, a large number of substituted polyanilines have been prepared. The sulfonated form of PANI is water soluble, and can be prepared by treatment of PANI with fuming sulfuric acid (31). A variety of other soluble substituted AJ-alkylsulfonic acid self-doped derivatives have been synthesized that possess moderate conductivity and allow facile preparation of spincoated thin films (32). 

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. 

Oxidation of aniline with a mixture of manganese dioxide and sulfuric acid has been used commercially for production of -benzoquinone [106-51-4] (35). 

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). 

Historically, the first condnctive polymer was prepared along route (2) but at the time not recognized Letheby in 1862 ( ) subjected aniline to anodic oxidation in sulfuric acid. 

The traditional unpredictably violent nature of the Skraup reaction (preparation of quinoline and derivatives by treating anilines with glycerol, sulfuric acid and an oxidant, usually nitrobenzene) is attributed to lack of stirring and adequate temperature control in many published descriptions [1], A reaction on 450 1 scale, in which sulfuric acid was added to a stirred mixture of aniline, glycerol, nitrobenzene, ferrous sulfate and water, went out of control soon after the addition. A 150 mm rupture disk blew out first, followed by the manhole cover of the vessel. The violent reaction was attributed to doubling the scale of the reaction, an unusually high ambient temperature (reaction contents at 32°C) and the accidental addition of excess acid. Experiment showed that a critical temperature of 120°C was attained immediately on addition of excess acid under these conditions [2],... 

Modern methods of manufacturing this probably oldest representative among synthetic organic pigments involve dissolving aniline in strong sulfuric acid. Oxidation is achieved with sodium dichromate in the presence of a copper salt or one of the above-mentioned oxidation catalysts. Oxidation with sodium chlorate initially affords an indamine polymer (pernigraniline) ... 

Of the above methods, the only ones which need be considered are those in which a mixture of aniline, glycerol and sulfuric acid is heated with an oxidizing agent. With the use of nitrobenzene, the reaction, according to the original method, takes place with extreme violence. 

Since the work was carried out, a method has been published 7 in which aniline, glycerol and sulfuric acid are treated with ferric oxide. By this method Adams and Parks were unable to obtain yields comparable with those resulting from the above directions. 

Quinone may be prepared by the oxidation of aniline with dichromate or manganese dioxide and sulfuric acid.1 This is a more feasible commercial method than the one given. However, the oxidation of hydroquinone is more rapid and convenient and, hence is more desirable for use in the laboratory. Various materials have been oxidized by chemical means to give quinone they are quinic acid,2 hydroquinone,3 benzidine,4 -phenylene-diamine,5 sulfanilic acid,6 / -phenolsulfonic acid,7 arbutin,8 aniline black,9 and the leaves of various plants.10 Quinone is also formed by several other methods by the fermentation of fresh grass 11 by the action of iodine on the lead salt of hydroquin-... 

Skraup synthesis org chem A method for the preparation of commercial synthetic quinoline by heating aniline and glycerol in the presence of sulfuric acid and an oxidizing agent to form pyridine unsubstituted quinolines. skraup sin-tha-sas slaked lime See calcium hydroxide. slakt iTm )... 

The most general method for synthesizing quinolines employs aniline or a substituted aniline, glycerol, sulfuric acid, and an oxidizing agent such as a ferric... 

Dichloronitrobenzene, Aniline, 2103 2,4,-Dichloronitrobenzene, Acetic acid, Potassium fluoride, Dimethylacetamide, 2104 t Ethylene oxide. Glycerol, 0829 t Ethylene oxide. Ammonia, 0829 t Formaldehyde, Phenol, 0416 Nitric acid, Formic acid, Urea, 4436 Nitric acid, Nitrobenzene, Sulfuric acid, 4436 Nitric acid, 1-Nitronaphthalene, Sulfuric acid, 4436 Sodium molybdate, 4713... 

Manganese(IV) oxide reacts with aniline in the presence of sulfuric acid forming quinone, an intermediate product in the manufacture of hydro-quinone ... 

Monopersulfuric acid (monoperoxysulfuric acid, H2SO5, Caro s acid) was first detected during electrolysis of sulfuric acid . Later, in 1898, Caro found the oxidation of aniline to nitrobenzene with ammonium peroxydisulfate Ic in H2SO4. Later, the oxidizing species was found to be 112805. ... 

Suspension of the metal oxide (CuO, CofOH)2, 552 or Ni(OH)2) in a mixture of ethylene glycol, aniline, and sulfuric acid led to simultaneous metal cluster formation and polymerization... 

The major drawback of the usual diazotization with alkaline nitrite lies in the production of two moles of water per mole of aniline. As in such conditions water is responsible for phenolic byproducts and rapid corrosion of vessels, several modifications have been recommended. The first is the addition, before sodium nitrite, of a dehydrating compound, such as concentrated sulfuric acid (used in an equimolar amount with respect to aniline),47 phosphoric oxide,48 or water-sensitive halides (PC15, SbCl5, BF3, etc., with MX /ArNH2 1 2).48 The second, which is more expensive, involves diazotization agents which deliver only one mole of water per mole of aniline. 

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