[pantsboy]

I don't know how accurate my reasoning or logic of this is since I not really basing it on anything I've read so far.  I was theorizing that one of the reasons Cl^- (for example) is a weak base in water is because H₂O can form extremely tight solvent cages around the ion due to hydrogen bonding with itself which would stabilize Cl^- charge and reduce it's nucleophilicty and proton receiving abilities.  By the same mode of thinking, when placed in a non-polar solvent in absence of water however I'd expect it to have a much stronger ability to act as base and pick up protons that can be easily removed from other compounds since it is no longer being tightly solvated.  This reasoning many not work for Cl^- because it may just not have a very strong desire to be protonated but can it apply to any other weak bases?

[Dan]

Yup, this is a common observation. To look at it another way, HCl is less likely to ionise in a non-protic environment (since the anion is not solvated by H bonding) - ie the conjugate acid of chloride is more stable in a non-protic solvent (than a protic solvent), therefore chloride (the corresponding base) is a stronger base in a non-protic solvent.

One example I know numbers for is the phenoxide ion (which is actually a reasonable base, comparable to an amine). The pKa of phenol in water is ~10, whereas  in DMSO (dimethyl sulfoxide) it is ~19 - ie. phenoxide is 10⁹ times more basic in DMSO than in water, an enormous difference!

[orgopete]

Solvent effects are significant. I have learned this by searching for simple rate constants for some alkyl halides. I don't recall having found the existence of this type of data because solvent effects have such a large effect on rates.

However, even though phenol is much less acidic in DMSO, NaOH should be more than sufficient to deprotonate it as the pKa of H₂0 is 31.4 in DMSO.