Methanesulfonic acid is a colorless liquid with the chemical formula CH₃SO₃H. It is the simplest of the alkylsulfonic acids. Salts and ester

Ester

Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...

s of methanesulfonic acid are known as mesylate

Mesylate

In chemistry, a mesylate is any salt or ester of methanesulfonic acid . In salts, the mesylate is present as the CH3SO3− anion. When modifying the International Nonproprietary Name of a pharmaceutical substance containing the group or anion, the correct spelling is mesilate .Mesylate esters are a...

s. Methanesulfonic acid is used as an acid catalyst in organic reactions because it is non-volatile, strong acid that is soluble in organic solvents. Methanesulfonic acid is convenient for industrial applications because it is liquid at ambient temperature, while the closely related p-toluenesulfonic acid

P-Toluenesulfonic acid

p-Toluenesulfonic acid or tosylic acid is an organic compound with the formula CH3C6H4SO3H. It is a white solid that is soluble in water, alcohols, and other polar organic solvents. The 4-CH3C6H4SO2- group is known as the Tosyl group and is often abbreviated as Ts or Tos...

 (PTSA) is solid. However, in a laboratory setting, solid PTSA is more convenient.

Methanesulfonic acid may be considered an intermediate compound between sulfuric acid

Sulfuric acid

Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...

 (H₂SO₄), and methylsulfonylmethane

Methylsulfonylmethane

Methylsulfonylmethane is an organosulfur compound with the formula 2SO2. It is also known by several other names including DMSO2, methyl sulfone, and dimethyl sulfone. This colorless solid features the sulfonyl functional group and is considered relatively inert chemically...

 ((CH₃)₂SO₂), effectively replacing an -OH group with a -CH₃ group at each step. This pattern can extend no further in either direction without breaking down the -SO₂ group.

Methanesulfonic acid can be used in the generation of borane

Borane

In chemistry, a borane is a chemical compound of boron and hydrogen. The boranes comprise a large group of compounds with the generic formulae of BxHy. These compounds do not occur in nature. Many of the boranes readily oxidise on contact with air, some violently. The parent member BH3 is called...

 (BH₃). By reacting methanesulfonic acid with NaBH₄

Sodium borohydride

Sodium borohydride, also known as sodium tetrahydridoborate, is an inorganic compound with the formula NaBH4. This white solid, usually encountered as a powder, is a versatile reducing agent that finds wide application in chemistry, both in the laboratory and on a technical scale. Large amounts are...

 in an aprotic solvent such as THF

Tetrahydrofuran

Tetrahydrofuran is a colorless, water-miscible organic liquid with low viscosity at standard temperature and pressure. This heterocyclic compound has the chemical formula 4O. As one of the most polar ethers with a wide liquid range, it is a useful solvent. Its main use, however, is as a precursor...

 or DMS

Dimethyl sulfide

Dimethyl sulfide or methylthiomethane is an organosulfur compound with the formula 2S. Dimethyl sulfide is a water-insoluble flammable liquid that boils at and has a characteristic disagreeable odor. It is a component of the smell produced from cooking of certain vegetables, notably maize,...

, the complex of BH₃ and the solvent is formed.