dimetylosulfat

Dimethyl sulfate, with the formula C2H6SO4, is a sulfonate ester derived from sulfuric acid in which both hydroxyl groups are replaced by methyl groups. It is a colorless to pale yellow, viscous liquid that is volatile at room temperature and has a strong, penetrating odor. It is highly reactive as a methylating agent and is used to introduce methyl groups into a range of substrates, including phenols, carboxylic acids as methyl esters, and amines.

In organic synthesis, dimethyl sulfate transfers a methyl group to nucleophiles, yielding methyl ethers or methylated amines. Reactions with phenols give aryl methyl ethers; with carboxylates, methyl esters are formed; with amines, dimethylation can occur, potentially forming quaternary ammonium salts under excess reagent. The compound is usually handled under strictly controlled conditions, typically in a fume hood, with appropriate personal protective equipment.

Dimethyl sulfate is moisture sensitive; on contact with water it hydrolyzes to methanol and sulfuric acid:

(CH3O)2SO2 + 2 H2O → 2 CH3OH + H2SO4

Because of its extreme toxicity and potential risks to health, dimethyl sulfate is subject to regulation and is typically available only to trained personnel and through controlled suppliers. Safer alternatives exist for many methylation applications, but dimethyl sulfate remains valuable for certain selective transformations in research and industry.