Methyl bisulfate is a chemical compound with the molecular formula (CH3)HSO4. This compound is the mono-methyl ester of sulfuric acid. Its structure is CH3−O−S(=O)2−OH. 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 → HSO4 + CH3OH