Methyl bisulfate is a chemical compound with the molecular formula CH4O4S. This compound is the mono-methyl ester of sulfuric acid. The significance of methyl bisulfate is that it is an intermediate in the hydrolysis of the important reagent dimethyl sulfate, (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 1993 with the discovery that certain mercury compounds catalyze the conversion of methane to methylbisulfate in good yields with excellent selectivity in concentrated sulfuric acid.