Aniline sulphate

On acetylation it gives acetanilide. Nitrated with some decomposition to a mixture of 2-and 4-nitroanilines. It is basic and gives water-soluble salts with mineral acids. Heating aniline sulphate at 190 C gives sulphanilic add. When heated with alkyl chlorides or aliphatic alcohols mono- and di-alkyl derivatives are obtained, e.g. dimethylaniline. Treatment with trichloroethylene gives phenylglycine. With glycerol and sulphuric acid (Skraup s reaction) quinoline is obtained, while quinaldine can be prepared by the reaction between aniline, paraldehyde and hydrochloric acid. 

It is prepared by heating aniline sulphate for 8 hours at l C. It readily diazotizes and is used as first component in a large variety of azo dyes. 

Dissolve 5 g. (5 ml.) of aniline in 50 ml. of warm dilute sulphuric acid in a conical flask and add 50 ml. of water. Place a thermometer in the solution, immerse the flask in a mixture of ice and water, and cool until the temperature of the stirred solution falls to 5°. Dissolve 4-5 g. of powdered sodium nitrite in 20 ml. of water, and add this solution in small quantities (about 2-3 ml. at a time) to the cold aniline sulphate solution. Keep tne latter well shaken and maintain the temperature at about 5° (see p. 183). When all the sodium nitrite solution has been added, transfer about 5 ml. of the cold solution to a test-tube for each of the following reactions. The remainder of the diazonium hydrogen sulphate solution must be kept in ice-water until required, and then when all the reactions have been carried out, the solution should be poured down the sink. 

Diazonium salts couple readily with aromatic primary amines, giving diazoamino compounds. If for instance an aqueous solution of aniline sulphate is diazotised with a deficiency of nitrous acid, only part of it is converted into benzenediazonium sulphate and the latter then couples with the unchanged aniline to give diazoaminobenzene. The reaction is carried out at the opti-CeHsNHj.HjSO + HONO = CbHsNjHSO, + zHaO... 

SULPHONATION OF AROMATIC AMINES If aniline is treated with excess of concentrated sulphuric acid and the resulting mixture, which contains aniline sulphate, is heated at 180° until a test portion when mixed with sodium hydroxide solution no longer liberates aniline, p-aminobenzenesulphonic acid or sulphanilic acid is formed this separates as the dihydrate upon pouring the cooled mixture into water. The reaction prohahly proceeds as follows ... 

If 40 ml. of 10 per cent, oleum be cautiously added to the aniline sulphate mixture, sulphonation proceeds much more rapidly and the time of heating is reduced from 5 hours to 1 hour. 

The cymidin is now sulphonated, 100 parts by weight of cymidin being slowly added to 69 parts by weight of sulphuric acid (sp. gr. 1 84), contained in a shallow dish, and the solid crystalline mass of cymidin sulphate thus obtai ed is then converted into cymidin sulphonic acid by an identical method to that tised in the so-called baking process for the preparation of stilphanilic acid from aniline sulphate. 

Hydrolysis of benzanilide. Place 5 g. of benzanilide and 50 ml. of 70 per cait. sulphuric acid in a small flask fitted with a reflux condenser, and boil gently for 30 minutes. Some of the benzoic acid will vapourise in fbe steam and solidify in the condenser. Pour 60 ml. of hot water down the condenser this will dislodge and partially dissolve the benzoic acid. Cool the flask in ice water filter off the benzoic acid (aniline sulphate does not separate at this dilution), wash well with water, drain, dry upon filter paper, and identify by m.p. (121°) and other tests. Render the filtrate alkaline by cautiously adding 10 per cent, sodium hydroxide solution, cool and isolate the aniline by ether extraction. Recover the ether and test the residue for aniline (Section IV, 100). 

Lignin gives characteristic colour reactions. With phlorogludnol and hydrochloric acid it turns red, with aniline sulphate, yellow. 

Sulphuric Acid (Aniline Sulphate). A solution of I gm. of csnlpluuiilie acid in 2fi ee. of boiling water should not change in appearance on adding a few drops of l>uriuin chloride solution. 

If either the o- or -position is occupied, only one isomer is obtained transformation to the mefo-position does not occur. This is a standard method of preparation of acyl-amino-ketones, or by a further hydrolysis of amino-ketones. The tendency, illustrated in this reaction, of groups to wander from the amino group to the nucleus, is also shown in previous reactions and in the preparation of aminoazobenzene from diazoamino-benzene (Preparation 456), of sulphanilic acid from aniline sulphate (Preparation 292), of o- and p-chloroacetanilides from acetochloranilide (Preparation 328), of o- and p-toluidine from methylaniline hydrochloride, and of 1 2 4-aminodimethylbenzene (2 4-xylidine) from dimethylaniline hydrochloride. 

Method I.—20 gms. of aniline are gradually added to 65 gms. of cone, sulphuric acid placed in a round-bottomed flask. Much heat is developed, and the contents of the flask should be cooled when the aniline is being added. The flask which contains aniline sulphate and excess cone, sulphuric acid is now heated on an oil or paraffin bath to 185° for about 5 hours. When a test portion, treated with dilute caustic soda solution, liberates no free aniline, the sulphonation is complete. The contents of the flask, after cooling, are poured into cold water, when the sulphanilic acid separates, usually as discoloured crystals. These are filtered off and recrystallised from water, adding a little animal charcoal, if necessary. A further crop can be obtained from the mother liquor. 

Nitroanilines may also be obtained by direct nitration of aniline (Bruns [7]), provided that a solution of aniline sulphate in sulphuric acid is prepared first, and then carefully introduced into a mixture of nitric acid with concentrated sulphuric acid. A condition necessary for success is that the reaction temperature must not exceed 0°C. 

Aniline sulphate test, (C6H5.NH2)2H2S04 A small quantity of the solid chlorate (say, 0 05 g) (DANGER) is mixed with 1 ml concentrated sulphuric acid, and 2-3 ml aqueous aniline sulphate solution added a deep-blue colour is obtained (distinction from nitrate). 

Aniline sulphate (1 %). Dissolve 1 g aniline sulphate (C6H5NH2)2-H2S04 in 100 ml of water. 

Sulphate conjugates are formed with hydroxy compounds (e.g. alcohols and phenols) or aromatic amines. For example, morphine-3-(9-ethereal sulphate is a minor metabolite of morphine and N-phenylsulphamic acid is a metabolite of aniline. Sulphate conjugates are strong acids and are readily excreted in the urine they are of relatively little importance in drug metabolism. 

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