4- Aminobenzenesulphonic acid,

Orthanilic acid (2-aminobenzenesulphonic acid) [88-21-1] M 173.2, m >300 (dec). Crystd from aqueous soln, containing 20ml of cone HCl per L, then crystd from distilled water. 

Aminobenzenesulphonic acid (orthanilic acid, Expt 6.64) is readily prepared by the reduction of 2-nitrobenzenesulphonic acid. The latter may be prepared by the hydrolysis of the corresponding sulphonyl chloride which is obtained from di-o-nitrophenyl disulphide. The preparation of this disulphide involves the use of the reactive aryl halide, 2-chloronitrobenzene (cf. Expts 6.93... 

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 ... 

Certain substituents (e.g. the amino group) may markedly affect the solubility and other properties of a sulphonic acid or a carboxylic acid. Thus such sulphonic acids as the aminobenzenesulphonic acids and the pyridine- and quinoline-sulphonic acids exist in the form of inner salts or dipolar ions that result from the interaction of the basic amino group and the acidic sulphonic acid group. Sulphanilic acid, for example, is more accurately represented by formula (1) than by formula (2)-. 

Experiment 6.65 METANILIC ACID (3-Aminobenzenesulphonic acid) Ph-NO, 220+ w-0,N-C6H4-S0,H Fc/ )0> m-H,N-C6H4-SOf... 

Direct irradiation of 9-dimethylsulphonium fluorenylide (141) in acetonitrile or tetrahydrofuran yields primarily the Stevens rearrangement product 9-methyl-9-(methylthio)fluorene (142), and a 1,2-shift of a sulphonic acid group is thought to be involved in the photoisomerization of the sodium salt of metanilic acid (m-aminobenzenesulphonic acid). Photoinduced rearrangement of 4,5-(ethylenedithio)-1,3-dithiole-2-thione (143) to the... 

We have tacitly accepted the numerical values and their evaluation of the heats of sublimation of 4-aminobenzoic acid and 4-aminobenzenesulphonic acid presented in Chickos recent compendium (see Reference 24). 

Vrba and Allan investigated the sulphonation of aniline and also the rearrangement of phenylsulphamic acid. In H2S04 phenylsulphamic acid rearranges to 2- and 4-aminobenzenesulphonic acids (equation 2), and gives an identical distribution of the 2-... 

Aminonaphthalenesulphonic acids and AT-naphthylsulphamic acids appear to be involved in similar types of processes as the aminobenzenesulphonic acids and N-... 

C. M. A. Brett, C. Thiemann, Conducting polymers from aminobenzoic acids and aminobenzenesulphonic acids influence of pH on electrochemical behaviour, of Electroanalytical Chemistry 2002, 538, 215. 

C. Thiemann, C. M. A. Brett, Electropolymerisation and properties of conducting polymers derived from aminobenzenesulphonic acids and from mixtures with aniline, Synthetic Metals 2001, 125, 445. 

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