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Methanesulfonyl chloride

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Title: Methanesulfonyl chloride  
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Subject: List of UN numbers 3201 to 3300
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Methanesulfonyl chloride

Methanesulfonyl chloride
CAS number 124-63-0 YesY
ChemSpider 29037 N
Jmol-3D images Image 1
Molecular formula CH3ClO2S
Molar mass 114.55 g mol−1
Appearance Liquid
Density 1.480 g/mL
Boiling point

161 °C, 434 K, 322 °F (730 mmHg)

Solubility in water Reacts[1][2]
Main hazards Lachrymator, highly toxic, corrosive
Related compounds
Other anions Methanesulfonyl fluoride
 N (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Methanesulfonyl chloride (mesyl chloride) is a compound containing a sulfonyl chloride used to make methanesulfonates and to generate sulfene.

Preparation, manufacture and handling

Methanesulfonyl chloride is highly toxic, moisture sensitive, corrosive, and a lachrymator. It should be stored in a dry location, preferably in a desiccator. It is manufactured either via direct synthesis from methane and sulfuryl chloride in a radical reaction (1):

CH4 (g) + SO2Cl2 (g) → CH3SO2Cl + HCl (g) (1)

Another method of manufacture starts with methanesulfonic acid, which is accessible from methane and sulfur trioxide (2) or by vigorous oxidation of methanethiol (3):

CH4 (g) + SO3 (g) → CH3SO3H (l) (2)
CH3SH + HNO3 → CH3SO3H + H2O + NOx (3)

The methanesulfonic acid prepared is reacted with thionyl chloride (4) or phosgene (5) to form methanesulfonyl chloride:

CH3SO3H + SOCl2 → CH3SO2Cl + SO2 + HCl (4)
CH3SO3H + COCl2 → CH3SO2Cl + CO2 + HCl (5)



The main use of methanesulfonyl chloride is the formation of methanesulfonates from alcohols in the presence of a non-nucleophilic base.[3] Methanesulfonates are used as intermediates in substitution reactions, elimination reactions, reductions, and rearrangement reactions. When treated with a Lewis acid, oxime methanesulfonates will undergo a facile Beckmann rearrangement.[4]

Methanesulfonates have been occasionally used as a protecting group for alcohols. It is stable to acidic conditions and is cleaved back to the alcohol using sodium amalgam.[5]


Methanesulfonyl chloride will react with amines to form a methanesulfonamide. Unlike a methanesulfonate, a methanesulfonamide is a very stable functional group 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.[6]

Addition to alkynes

In the presence of copper(II) chloride, methanesulfonyl chloride will add across alkynes to form β-chloro sulfones.[7]

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.[8]


Forming acyliminium ions from α-hydroxyamides can be done using methanesulfonyl chloride and a base, typically triethylamine.[9]


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