Describe the sulphonation reaction of aniline, including the major product formed and the conditions required for its synthesis.

The sulphonation of aniline involves the addition of a sulfonic acid group (-SO₃H) to the aromatic ring. The major product is para-aminobenzenesulfonic acid (p-ABSA). The reaction requires concentrated sulfuric acid (H₂SO₄) as both a solvent and a reagent. Aniline is slowly added to the acid with cooling to control the reaction temperature. The sulfonation occurs at the para position due to the directing effect of the amino group. The resulting p-ABSA is water-soluble and serves as an important intermediate in the synthesis of dyes, pharmaceuticals, and other organic compounds.