4-methylsulfonyl chloride (commonly abbreviated as TosCl or TsCl) is a compound of CH3C6H4SO2Cl. This compound is a white solid with a foul odor and is widely used in organic synthesis, manufacturing dyes, saccharin, etc. This compound belongs to the derivative of sulfonyl chloride. Currently, due to environmental issues, there is a shortage of construction in China, and the market has been relatively tight.