Benzenesulfonyl chloride is prepared by reaction of benzene and chlorosulfonic acid or from the sodium salt of benzenesulfonic acid and PCl₅ or POCl₃. It reacts with Grignard reagent from N-unsubstituted indoles to form oxindoles or substituted indoles. Benzenesulfonyl chloride is the derivatization reagent for the determination of various amines in waste water and surface water at the sub-ppb level by gas chromatography-mass spectrometry.

Benzenesulfonyl chloride may be used to develop fast, accurate and reproducible method for thiamine assay in different food products. It is useful reagent for preparing α-disulfones.