Methyl fluorosulfonate

Methyl fluorosulfonate, also known as magic methyl, is the organic compound with the formula FSO₂OCH₃. It is a colorless liquid that is used as a strong methylating agent in organic synthesis. Because of several fatal industrial accidents involving this compound, it has largely been replaced by the related reagent methyl trifluoromethanesulfonate.

Synthesis and reactions

It is prepared by distillation of an equimolar mixture of fluorosulfonic acid and dimethyl sulfate. It was originally produced by the reaction of methanol with fluorosulfonic acid.
Methyl fluorosulfonate is a highly electrophilic reagent for methylation. It is ranked as less powerful than methyl trifluoromethanesulfonate.

Toxicity

Toxicity of this reagent is equivalent to that of phosgene with an inhaled LC₅₀ of about 5 ppm. Several cases of poisoning resulting in death from pulmonary edema have been reported.