Orientation and reactivity in nucleophilic replacement in polyfluoro-benzenes and -pyridines

Rate measurements for reactions of ammonia with polyfluopyridines and methoxide with polyfluorobenzenes indicate that the activating influence of fluorine, with respect to the point of nucleophilic attack, is in the order: meta > ortho > para. This leads to a more complete explanation of the orientation of nucleophilic substitution in polyfluoro-benzenes and -pyridines than the generally accepted one.