When looking for a compound that is the most reactive with a nucleophile do you always choose the molecule that is the least electronegative?(No. Electronegativity refers to an atom rather than to a molecule. - GS) Would it be correct if I had said: the most reactive compound with a nucleophile is the molecule that contains  the least electronegative atom because this reaction will lead to the best leaving group? (No. Most electronegative atom makes the weakest base if you compare elements of the same period with the same charge. - GS).