The electronic parameters of a series of mono- and difluoro aromatic compounds have been calculated by the quantum semiempirical method PM3. From these calculations, a relationship has been established between the charge on the aromatic carbon ipso to the fluorine and the reactivity of these compounds with hard nucleophiles, such as phenolate ions, to give aromatic ethers. A good correlation can also be established between charge on C-ipso and the C-13 and F-19 NMR chemical shifts, used previously to measure the reactivity of fluorine compounds in the above indicated reaction.