sulfonyl chloride (CAS NO.: ) could be produced through the following synthetic route.

In a 1-l. three-necked flask fitted with a mechanical stirrer, a reflux condenser, a thermometer, and a separatory funnel, and set up in a hood, is placed 152 g. (105 ml., 1.5 moles) of methanesulfonic acid (Note 2). The acid is heated to 95° on a steam bath, and 238 g. (146 ml., 2.0 moles) of chloride is added over a period of 4 hours. The temperature is kept at 95° throughout the addition and for 3.5 hours after it is completed.

The product is transferred to a modified Claisen flask and distilled under reduced pressure, heat being supplied by an oil bath. Most of the thionyl chloride distils at room temperature. The yield of almost colorless product distilling at 64–66°/20 mm. is 122–143 g. (71–83%); n_D23 1.451.