98-61-3

The preparation of 4-iodobenzenesulfonyl chloride is as follows: 2.5 L of chloroform and chlorosulfonic acid (503 g, 4.32 mol) were added to a dry 5 L three-necked round-bottom flask equipped with a mechanical stirrer, a heating hood, and a water-cooled condenser. The condenser's connecting hose was connected to a 2 L feeding funnel and an inert gas inlet. The mixture was heated to mild reflux, and a solution of iodobenzene (400 g; 1.96 mol) in 0.5 L of chloroform was added over 1 hour. During this time, the color of the reaction mixture changed from yellow to deep red-purple with the release of HCl. The reaction was then heated under reflux for another hour. GC analysis showed complete conversion to p-iodobenzenesulfonyl chloride. The mixture was poured into a 6 L separatory funnel, and the lower layer, mostly composed of inorganic acid, was discarded for post-treatment. The organic layer was neutralized and dried over MgSO₄. Solvent evaporation yielded 4-iodobenzenesulfonyl chloride as a crude yellow solid; yield approximately 593 g (quantitative). If desired, the product can be further purified by distillation under high vacuum.