Sulfuric acid, aniline salt

The older methods have been replaced by methods which require less, if any, excess sulfuric acid. For example, sulfonation of naphthalene can be carried out in tetrachloroethane solution with the stoichiometric amount of sulfur trioxide at no greater than 30°C, followed by separation of the precipitated l-naphthalenesulfonic acid the filtrate can be reused as the solvent for the next batch (14). The purification of 1-naphthalenesulfonic acid by extraction or washing the cake with 2,6-dimethyl-4-heptanone (diisobutyl ketone) or a C-1—4 alcohol has been described (15,16). The selective insoluble salt formation of 1-naphthalenesulfonic acid in the sulfonation mixture with 2,3-dimethyl aniline has been patented (17). 

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) ... 

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-... 

For weakly basic amines, i.e. anilines with poly nitro groups, e.g. 2, 4,-dintro-6-bromoaniline, and also most heterocyclic amines, an alternative method must be adopted using nitrosylsulfuric acid. This diazotising medium can be made by dissolving sodium nitrite in concentrated sulfuric acid, but is also available preformed from chemical suppliers. The weakly basic amine is added gradually to the nitrosyl-sulfuric acid with cooling, and after reaction is complete the mixture is poured into ice and water to give a solution of the diazonium salt. 

The reaction of 9-amino- 1-phenaleneimine 453 with thiony(aniline results in the corresponding thiadiazine 5-oxide 454, which is protonated in sulfuric acid and then dehydrated to give phenaleno[c[Pg.77]

Prepn is by heating 2,6-dinitro aniline with sulfuric acid. Tbs K salt, Potassjum-3,5-Dinitru-4-Amino Benzol Sulfonate KC6 H4N3S07 mw 301.29 N 13.95% OB to C02 —37.17% v si sol in w si sol in acet and ethanol, deflagrates on heating Ref Beil 14,710... 

There are only two practical laboratory methods lor the production of isatin, viz. the oxidation of indigo,1 and the condensation of aniline, chloral hydrate, and hydroxylamine salts, followed by the action of sulfuric acid.2... 

Quinones can he prepared hy the oxidation of phenols, dihydroxy-henzenes, dimethoxyhenzenes and anilines. For example, 1,4-dihydroxy-henzene (hydroquinone) can he oxidized in good yield using sodium chlorate in dilute sulfuric acid in the presence of vanadium pentoxide and also hy manganese dioxide and sulfuric acid and hy chromic acid. Other reagents which convert hydroquinones to quinones include Fremy s salt [potassium nitrosodisulfonate, (KS03)2N0] and cerium(IV) ammonium nitrate [CAN, Ce(NH4)2(N03)J. 

Although protonation of the amine leads to the anilinium salt which is a deactivating substituent, nitration of aniline in nitric acid sulfuric acid yields 60% para and 34% meta substitution, whilst nitration of acetanilide gives 79% para and 19% ortho nitroacetanilides. 

The presence of an amino group on an aromatic ring often results in oxidation of the ring to a quinone. The classical and industrial method is the treatment of anilines with potassium dichromate and sulfuric acid. Thus, aniline at room temperature is converted into p-benzoquinone in 86% yield [647], and 2,5-dimethylaniline at 80 °C gives a 55% yield of p-xyloquinone [648. A specific reagent for such oxidations is the Fremy salt, potassium nitrosodisulfonate (equation 528) [490. The oxidation of the amino group takes place even if it is acylated (equation 529) [1190. ... 

A) Benzenediazoniiim Sulfate (Solid). Place 1 ml of aniline in an eight-inch tube, and add 5 ml of ethanol (95 per cent) then very slowly add 1 ml of concentrated sulfuric acid. Rotate the tube and immerse it in cold water. Add drop by drop 1.5 ml of butyl or amyl nitrite at such a rate that the temperature is kept at 30-35°. Allow to stand for five minutes, and then immerse the tube in an ice bath. The crystals of the diazonium salt separate out. Filter the crystals with suction, using a micro funnel, and wash with a few milliliters of alcohol and then with 5 ml of ether. Dry with suction... 

D) Preparation of Methyl Orange. Add 2.6 g (0.015 moles) of sulfanilic acid to 20 ml of water, and then add 3 ml of 6 A sodium hydroxide solution. Warm slightly until solution is complete. Add 1 g of sodium nitrite, stir until the salt is dissolved, and cool to 25°. Pour this mixture, with constant stirring, into a beaker which contains 30 ml of water, 40 g of crushed ice, and 2 ml of concentrated sulfuric acid. Allow to stand for half an hour, adding ice if the temperature rises above 5°. Add a solution of 2 ml of dimethyl-aniline in 2 ml of hydrochloric acid. Stir, allow to stand for 15 minutes, and add 12 ml of 6 A sodium hydroxide and 50 ml of saturated salt solution. Cool for 10 minutes. Filter by suction, and wash the crystals with 10 ml of cold saturated salt solution. Press the crystals on the filter into a cake to drain well. To recrystallize, suspend the cake in 100-125 ml of distilled water and heat until solution is complete at 90-95°, adding more water if necessary. Filter the hot solution, and cool. Filter the crystals with suction, wash with alcohol and finally with ether. The yield is 3.5-4.0 g. 

Several chemical methods are used. In one method the mixture of aniline and quinoline is acylated either with acetic anhydride or with sulfochloride. The aniline forms a derivative and the quinoline remains unaffected. A second method treats the mixture with sodium nitrite and sulfuric acid. The aniline is converted into the diazonium salt and the quinoline forms the sulfate. The solution is made alkaline and steam-distilled the diazonium salt changes to sodium phenoxide, and quinoline is distilled. In the third method, the mixture is separated by means of hydrochloric acid and zinc chloride. Quinoline chlorozincate, (C9H7N)2H2ZnCl4, is sparingly soluble in water and is separated from the soluble anihne salt. 

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