Abstract The relative displacement rates of the halide substituent from 2-fluoro-and 2- chloropyridines by EtONa in EtOH at+ 25 were assessed by competition kinetics. The 2- fluoropyridine reacts 320 times faster than the chloro analog. A CF 3 group increases the reactivity more than single halogen atoms do, whatever the element, and the latter are superior to Me 3 Si groups. Substituents accommodated at the 4-position operate through ...