Quote: Originally posted by forgottenpassword | I recall reading that dimsyl sodium can be prepared (and reacted in situ) with DMSO/KOH. I suppose it could be classed as an "organometallic" compound
-- which is nevertheless very easy to prepare. I could find the paper if there is a specific interest. It is referenced in one of the Gaylord
bulletins, which I looked up. The use of alkoxides seems a more generally useful way to prepare it, though. |
No, sodium hydride is the reagent commonly used to prepare a solution of sodium dimsyl in DMSO. Supposedly sodium metal also works, but is obviously
not practical.
Alkali hydroxides or alkoxides will not do. The pKa of H2O in DMSO is 31.4, while DMSO in DMSO has a pKa of 35.1. As one would expect, MeOH
is more than 100 times more acidic in DMSO than water (pKa 29). Even t-BuOH in DMSO is not even ten times less acidic than water (pKa 32.2,
compare that to its aq. acidity!). This means that even t-BuOK would only give an equilibrium amount of potassium dimsyl, but would not give
full conversion. But making alkali dimsyl from alkali hydroxides or alkoxides by removing water or alcohols correspondingly at least does not sound as
nonsense. While making benzylalkalis from alkali hydroxides makes just as much sense as it appears to make sense. |