I was just doing a passage on kinetics, and one problem asked what would happen to the rate if CH3SH (the nucleophile) was replaced with methanol (for an SN2 reaction). The solution says that the reaction will occur more slowly. It says that methyl CH3SH is a stronger nucleophile than methanol because CH3SH is a stronger base. I am having trouble understanding why. I have always been told that CH3SH is a stronger ACID than methanol because of the larger radius; if this is the case, shouldn't it be less basic than methanol? Also, S is less electronegative than O. Can someone please help me out? I know the chances are slim that this would be on the MCAT, but I would like to know the answer for sanity, if anything. Thanks.