Dimethylsulfate

Dimethyl sulfate is a chemical compound with formula (CH₃O)₂SO₂. As the diester of methanol and sulfuric acid, its formula is often written as (CH₃)₂SO₄ or even Me₂SO₄, where CH₃or Me is methyl. Me₂SO₄ is mainly used as a methylating agent in organic synthesis.

Under standard conditions, Me₂SO₄ is a colourless oily liquid with a slight onion-like odour (although smelling it would represent significant exposure). Like all strong alkylating agents, Me₂SO₄ is highly toxic. Its use as a laboratory reagent has been superseded to some extent by methyl triflate, CF₃SO₃CH₃, the methyl ester of trifluoromethanesulfonic acid.