<unk>  is a chemical compound with formula (CH3O)2SO2.   As the dimethyl ester of sulfuric acid. Its formula is often written as (CH3)2SO4 or even Me2SO4; where Me is methyl, or CH3.  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. 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 Its use as a laboratory reagent has been superseded to some extent by methyl triflate, CF3SO3CH3, the methyl ester of trifluoromethanesulfonic acid.
Dimethyl sulfate
Vinyl bromide
Palifermin
Dimethylcarbate
Pentifylline
Trichloroethylene
Methylenedioxymethcathinone
Tetrachloroethylene