[EdwardX]

Since alcohols are stronger bases than thiols, you would expect alcohols to be better nucleophiles in substitution and elimination reaction than thiols!  But because sulfur is larger than oxygen it is less solvated by a protic solvent, and because it is more polarizable, it is actually a better nucleophile(in protic solvents).  My question is:  Are thiols still better nucleophiles in aprotic solvent?  Or does the lesser solvation of alcohols in aprotic solvents, cause the more electronegative alcohol to be the better nucleophile?