Methanesulphonic acid

Methanesulfonic acid (MsOH) is a colorless liquid with the chemical formula CH₃SO₃H. It is the simplest of the alkylsulfonic acids. Salts and esters of methanesulfonic acid are known as mesylates (or methanesulfonates, as in ethyl methanesulfonate). It is hygroscopic in its concentrated form. Methanesulfonic acid may be considered an intermediate compound between sulfuric acid (H₂SO₄), and methylsulfonylmethane ((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 dissolve a wide range of metal salts, many of them in significantly higher concentrations than in hydrochloric or sulfuric acid.

Applications

Methanesulfonic acid is used as an acid catalyst in organic reactions because it is a non-volatile, strong acid that is soluble in organic solvents. It is convenient for industrial applications because it is liquid at ambient temperature, while the closely related p-toluenesulfonic acid (PTSA) is solid. However, in a laboratory setting, solid PTSA is more convenient.

Methanesulfonic acid can be used in the generation of borane (BH₃) by reacting methanesulfonic acid with NaBH₄ in an aprotic solvent such as THF or DMS, the complex of BH₃ and the solvent is formed.

Electroplating

Solutions of methanesulfonic acid are used for the electroplating of tin and tin-lead soldiers. It is displacing the use of fluoroboric acid, which releases corrosive and volatile hydrogen fluoride.Methanesulfonic acid is also a primary ingredient in rust and scale removers. It is used to clean off surface rust from ceramic, tiles and porcelain which are usually susceptible to acid attack.