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Methanesulfonyl chloride

Methanesulfonyl chloride
IUPAC name Methanesulfonyl chloride
Other names Mesyl chloride
CAS number 124-63-0
Molecular formula CH3ClO2S
Molar mass 114.56 g/mol
Appearance liquid
Density 1.480 g/mL
Boiling point

60 °C (21 mm Hg)

Main hazards Lachrymator,
Highly toxic,
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Methanesulfonyl 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 dry location, preferably in a dessicator. It is manufactued either via direct synthesis from methane and sulfuryl chloride in a radical reaction (1):

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

other method of manufacture starts with methanesulfonic acid, which is accessible out of 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)

methanesulfonic acid prepared is reacted with thionyl chloride (4) or phosgene (5) to form mesyl 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 and a non-nucleophilic base.[1] 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.[2]

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.[3]


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.[4]

Addition to alkynes

In the presence of copper(II) chloride, methanesulfonyl chloride will add across alkynes to form β-chloro sulfones.[5]

Formation of heterocycles

Upon treatment with a base, such as triethylamine, methanesulfonyl chloride will undergo an alpha-elimination to form sulfene. Sulfene can undergo cycloadditions to form various heterocycles. α-Hydroxyketones react with sulfene to form five-membered sultones.[6]


Forming acyliminium ions from α-hydroxyamides can be done using methanesulfonyl chloride and a base, typically triethylamine.[7]


  1. ^ Furst, A.; Koller, F. Helv. Chim. Acta 1947, 30, 1454.
  2. ^ Maruoke, K.; Miyazaki, T.; Ando, M.; Matsumura, Y.; Sakane, S.; Hattori, K.; Yamamoto, H. J. Am. Chem. Soc. 1983, 105, 2831.
  3. ^ Webster, K. T.; Eby, R.; Schuerch, C. Carbohydr. Res. 1983, 123, 335.
  4. ^ Merlin, P.; Braekman, J. C.; Daloze, D. Tetrahedron Lett. 1988, 29, 1691.
  5. ^ Amiel, Y. Tetrahedron Lett. 1971, 661.
  6. ^ Potonay, T.; Batta, G.; Dinya, Z. J. Heterocycl. Chem. 1988, 25, 343.
  7. ^ Chamgerlin, A. R.; Nguyen, H. D.; Chung, J. Y. L. J. Org. Chem. 1984, 49, 1682.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Methanesulfonyl_chloride". A list of authors is available in Wikipedia.
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