Methanesulfonyl chloride
chemical compound
Methanesulfonyl chloride (mesyl chloride) is an organosulfur compound with the formula CH3SO2Cl. Using the organic pseudoelement symbol Ms for the methanesulfonyl (or mesyl) group CH3SO2–, it is frequently abbreviated MsCl in reaction schemes or equations. It is a colourless liquid that dissolves in polar organic solvents but is reactive toward water, alcohols, and many amines. The simplest organic sulfonyl chloride, it is used to make methanesulfonates and to generate the elusive molecule sulfene (methylenedioxosulfur(VI)).
Preparation
It is produced by the reaction of methane and sulfuryl chloride in a radical reaction:
CH4 + SO2Cl2 → CH3SO2Cl + HCl
Another method of production entails chlorination of methanesulfonic acid with thionyl chloride or phosgene:
CH3SO3H + SOCl2 → CH3SO2Cl + SO2 + HCl
CH3SO3H + COCl2 → CH3SO2Cl + CO2 + HCl
Reactions
Methanesulfonyl chloride is a precursor to many compounds because it is highly reactive. It is an electrophile, functioning as a source of the "CH3SO2+" synthon.
Methanesulfonates
Methanesulfonyl chloride is mainly used to give methanesulfonates by its reaction with alcohols in the presence of a non-nucleophilic base. 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.
Methanesulfonates are used as intermediates in substitution reactions, elimination reactions, reductions, and rearrangement reactions.
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