Dimethyl sulfite is prepared from a 1:2 ratio of
thionyl chloride and methanol. The reaction can be catalyzed by tertiary amine bases and likely proceeds via the chlorosulfinate (MeOS(O)Cl), this intermediate will exist only fleetingly in the presence of methanol and as such its decomposition to
methyl chloride and
sulfur dioxide (via the slower
SNi mechanism) is not observed to any great extent. : ==See also==