Using the organic pseudoelement symbol Ms for the methanesulfonyl (or mesyl) group CH3SO2–, it is frequently abbreviated MsCl in reaction schemes or equations.

The simplest organic sulfonyl chloride, it is used to make methanesulfonates and to generate the elusive molecule sulfene (methylenedioxosulfur(VI)).

[8] In contrast to the formation of toluenesulfonates from alcohols and p-toluenesulfonyl chloride in the presence of pyridine, the formation of methanesulfonates is believed to proceed via a mechanism wherein methanesulfonyl chloride first undergoes an E1cb elimination to generate the highly reactive parent sulfene (CH2=SO2), followed by attack by the alcohol and rapid proton transfer to generate the observed product.

This mechanistic proposal is supported by isotope labeling experiments and the trapping of the transient sulfene as cycloadducts.

[7] When used as a protecting group, they can be converted back to amines using lithium aluminium hydride or a dissolving metal reduction.