Methanesulfonyl chloride

Methanesulfonyl chloride

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Names
IUPAC name Methanesulfonyl chloride
Other names Mesyl chloride
Identifiers
CAS Number	124-63-0 Y
ChemSpider	29037 N
Jmol 3D model	Interactive image
PubChem	31297
SMILES CS(Cl)(=O)=O
Properties
Chemical formula	CH3ClO2S
Molar mass	114.54 g·mol−1
Appearance	colorless liquid
Density	1.480 g/mL
Boiling point	161 °C (322 °F; 434 K) 730 mmHg
Solubility in water	Reacts
Vapor pressure	{{{value}}}
Related compounds
Other anions	Methanesulfonyl fluoride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Methanesulfonyl chloride (mesyl chloride) is an organosulfur compound with the formula CH₃SO₂Cl. 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.

Preparation

It is manufactured by the reaction of methane and sulfuryl chloride in a radical reaction:

CH₄ + SO₂Cl₂ → CH₃SO₂Cl + HCl

Another method of manufacture 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⁺" group.

Methanesulfonates

Methanesulfonyl chloride is mainly used to give methanesulfonates by its reaction alcohols in the presence of a non-nucleophilic base. Methanesulfonates are used as intermediates in substitution reactions, elimination reactions, reductions, and rearrangement reactions. When treated with a Lewis acid, oxime methanesulfonates undergo facile Beckmann rearrangement.

Methanesulfonates are occasionally used as a protecting group for alcohols. They are stable to acidic conditions and is cleaved back to the alcohol using sodium amalgam.

Methanesulfonamides

Methanesulfonyl chloride react with primary and secondary amines to give methanesulfonamide. Unlike a methanesulfonate, methanesulfonamides are very resistant toward hydrolysis under both acidic and basic conditions. When used as a protecting group, they can be converted back to amines using lithium aluminium hydride or a dissolving metal reduction.

Addition to alkynes

In the presence of copper(II) chloride, methanesulfonyl chloride will add across alkynes to form β-chloro sulfones.

Formation of heterocycles

Upon treatment with a base, such as triethylamine, methanesulfonyl chloride will undergo an elimination to form sulfene. Sulfene can undergo cycloadditions to form various heterocycles. α-Hydroxyketones react with sulfene to form five-membered sultones.

Miscellaneous

Forming acyliminium ions from α-hydroxyamides can be done using methanesulfonyl chloride and a base, typically triethylamine.

Safety

Methanesulfonyl chloride is toxic and moisture sensitive, corrosive, and a lachrymator.