Heats of formation [Δ f H o (RX)] for compounds of the type CH m (CH 3 ) 3−m X and differences in heats of formation [Δ f H o (CH m (CH 3 ) 3−m X)−Δ f H o (CH 3 X)], with m=1-3, are plotted against values of electronegativity obtained from 17 different scales