Fluoride ion in phosphoryl transfer. A catalyst or an inhibitor?

Abstract

Fluoride ions have been found to affect hydrolysis of aryl phosphates by more than one mechanism. For substrates with a leaving group like the anions of p-nitrophenol or the N methyl-8-hydroxyquinolinium ion, F^– accelerated the rate via fast formation and decay of the phosphorofluoridate intermediate. For a case when the reaction was autocatalysed (protonation of the leaving group by the acidic product), fluoride ion acted as a net inhibitor due to the elimination of acidic catalysis. The same effect was observed for the hydrolysis of dimethyl phosphorofluoridate. LiF was found to be much less effective in nucleophilic catalysis than other fluoride salts.