2-Amino-4-sulphobenzoic acid (I) is prepd. by reacting 2-nitrotoluene (II) and oleum, followed by oxidn. and redn. of the resultant 2-nitro-toluene-4-sulphonic acid (III). (II) and oleum contg. 30-80 wt.% SO3 are dosed synchronously and the reaction mixt. is oxidised and reduced to (I) under alkaline conditions without isolating (III). Also claimed is (I) prepd. in this way.
