Methanesulfonyl chloride (mesyl chloride) is an

organosulfur compound Organosulfur chemistry is the study of the properties and synthesis of organosulfur compounds, which are organic compounds that contain sulfur. They are often associated with foul odors, but many of the sweetest compounds known are organosulfur der ...

with the formula . Using the organic

pseudoelement symbol The skeletal formula, line-angle formula, bond-line formula or shorthand formula of an organic compound is a type of minimalist structural formula representing a molecule's atoms, bonds and some details of its geometry. The lines in a skeleta ...

Ms for the methanesulfonyl (or mesyl) group –, 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 In chemistry, a sulfonyl halide consists of a sulfonyl () group singly bonded to a halogen atom. They have the general formula , where X is a halogen. The stability of sulfonyl halides decreases in the order fluorides > chlorides > bromides > ...

, it is used to make methanesulfonates and to generate the elusive molecule sulfene (methylenedioxosulfur(VI)).Valerie Vaillancourt, Michele M. Cudahy, Matthew M. Kreilein and Danielle L. Jacobs "Methanesulfonyl Chloride" in E-EROS Encyclopedia for Reagents in Organic Synthesis

Preparation

It is produced by the reaction of

methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The abundance of methane on Earth makes ...

and

sulfuryl chloride Sulfuryl chloride is an inorganic compound with the formula SO2Cl2. At room temperature, it is a colorless liquid with a pungent odor. Sulfuryl chloride is not found in nature. Sulfuryl chloride is commonly confused with thionyl chloride, SOC ...

in a

radical reaction A free-radical reaction is any chemical reaction involving free radicals. This reaction type is abundant in organic reactions. Two pioneering studies into free radical reactions have been the discovery of the triphenylmethyl radical by Moses Gomb ...

: : Another method of production entails chlorination of

methanesulfonic acid Methanesulfonic acid (MsOH, MSA) or methanesulphonic acid (in British English) is an organosulfuric, colorless liquid with the molecular formula and structure . It is the simplest of the alkylsulfonic acids (). Salts and esters of methanesul ...

with

thionyl chloride Thionyl chloride is an inorganic compound with the chemical formula . It is a moderately Volatility (chemistry), volatile, colourless liquid with an unpleasant acrid odour. Thionyl chloride is primarily used as a Halogenation, chlorinating reagen ...

phosgene Phosgene is an organic chemical compound with the formula . It is a toxic, colorless gas; in low concentrations, its musty odor resembles that of freshly cut hay or grass. It can be thought of chemically as the double acyl chloride analog of ...

: : :

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 chemistry, an alcohol (), is a type of organic compound that carries at least one hydroxyl () functional group bound to a Saturated and unsaturated compounds, saturated carbon atom. Alcohols range from the simple, like methanol and ethanol ...

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 (), 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. Sulfene-mechanism

Methanesulfonates are used as intermediates in

substitution reaction A substitution reaction (also known as single displacement reaction or single substitution reaction) is a chemical reaction during which one functional group in a chemical compound is replaced by another functional group. Substitution reactions ar ...

elimination reaction An elimination reaction is a type of organic reaction in which two substituents are removed from a molecule in either a one- or two-step mechanism. The one-step mechanism is known as the E2 reaction, and the two-step mechanism is known as the E1 r ...

reductions Reductions (, also called ; ) were settlements established by Spanish rulers and Roman Catholic missionaries in Spanish America and the Spanish East Indies (the Philippines). In Portuguese-speaking Latin America, such reductions were also ...

, and

rearrangement reaction In organic chemistry, a rearrangement reaction is a broad class of organic reactions where the carbon skeleton of a molecule is rearranged to give a structural isomer of the original molecule. Often a substituent moves from one atom to another at ...

s. When treated with a

Lewis acid A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any ...

oxime In organic chemistry, an oxime is an organic compound belonging to the imines, with the general Chemical formula, formula , where R is an organic Side chain, side-chain and R' may be hydrogen, forming an aldoxime, or another organic functional g ...

methanesulfonates undergo facile

Beckmann rearrangement The Beckmann rearrangement, named after the German chemist Ernst Otto Beckmann (1853–1923), is a rearrangement reaction, rearrangement of an oxime functional group to substituted amides. The rearrangement has also been successfully performed on ...

. Methanesulfonates are occasionally used as a

protecting group A protecting group or protective group is introduced into a molecule by chemical modification of a functional group to obtain chemoselectivity in a subsequent chemical reaction. It plays an important role in multistep organic synthesis. In man ...

for alcohols. They are stable to acidic conditions and is cleaved back to the alcohol using

sodium amalgam Sodium amalgam, with the common formula Na(Hg), is an alloy of mercury and sodium. The term amalgam is used for alloys, intermetallic compounds, and solutions (both solid solutions and liquid solutions) involving mercury as a major component. ...

Methanesulfonamides

Methanesulfonyl chloride react with primary and secondary

amine In chemistry, amines (, ) are organic compounds that contain carbon-nitrogen bonds. Amines are formed when one or more hydrogen atoms in ammonia are replaced by alkyl or aryl groups. The nitrogen atom in an amine possesses a lone pair of elec ...

s to give methanesulfonamides. Unlike methanesulfonates, 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 Lithium aluminium hydride, commonly abbreviated to LAH, is an inorganic compound with the chemical formula or . It is a white solid, discovered by Finholt, Bond and Schlesinger in 1947. This compound is used as a reducing agent in organic synthe ...

or a dissolving metal reduction.

Addition to alkynes

In the presence of

copper(II) chloride Copper(II) chloride, also known as cupric chloride, is an inorganic compound with the chemical formula . The monoclinic crystal system, monoclinic yellowish-brown anhydrous form slowly absorbs moisture to form the orthorhombic blue-green hydrate, ...

, methanesulfonyl chloride will add across alkynes to form β-chloro sulfones.

Formation of heterocycles

Upon treatment with a base, such as

triethylamine Triethylamine is the chemical compound with the formula N(CH2CH3)3, commonly abbreviated Et3N. Like triethanolamine and the tetraethylammonium ion, it is often abbreviated TEA. It is a colourless volatile liquid with a strong fishy odor remini ...

, methanesulfonyl chloride will undergo an elimination to form sulfene. Sulfene can undergo

cycloaddition In organic chemistry, a cycloaddition is a chemical reaction in which "two or more Unsaturated hydrocarbon, unsaturated molecules (or parts of the same molecule) combine with the formation of a cyclic adduct in which there is a net reduction of th ...

s to form various heterocycles. α-Hydroxyketones react with sulfene to form five-membered sultones.

Miscellaneous

Forming acyliminium ions from α-hydroxy

amide In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a chemical compound, compound with the general formula , where R, R', and R″ represent any group, typically organyl functional group, groups or hydrogen at ...

s can be done using methanesulfonyl chloride and a base, typically

Safety

Methanesulfonyl chloride is highly toxic by inhalation,

corrosive Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engine ...

, and acts as a lachrymator. It reacts with nucleophilic reagents (including water) in a strongly exothermic manner. When heated to decomposition point, it emits toxic vapors of sulfur oxides and

hydrogen chloride The Chemical compound, compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colorless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hyd ...

References

{{Reflist Reagents for organic chemistry Sulfonyl halides Methyl compounds