Methyl bisulfate

Methyl bisulfate is CH3OSO3H. This compound is the combination of the hypothetical methyl cation and the bisulfate anion, written HSO4- but better described with the formula HOSO3-. The significance of (CH3)HSO4 is that it is an intermediate in the hydrolysis of the important reagent dimethylsulfate, (CH3)2SO4:
 * (CH3)2SO4 +  H2O  →  (CH3)HSO4  +  CH3OH

Methyl bisulfate is an acid:
 * (CH3)HSO4  →  (CH3)SO4-  +  H+

Methyl bisulfate came into the public view in 1998 with the discovery that certain platinum complexes catalyze the reaction of CH4 by SO3 and O2:
 * CH4 +  SO3  1/2 O2  →  (CH3)HSO4

This discovery pointed to a possible method for upgrading inexpensive and abundantly available methane (natural gas) into methanol, which is both a more useful chemical and more easily shipped than methane. The process is proposed to proceed via an intermediate containing the Pt-CH3 group.

Salts of (CH3)SO4- are commercially available, e.g. tris(2-hydroxyethyl)methylammonium methylsulfate (CAS #29463-06-7).