Which of the following leaving groups, when attached to a 2,4-dinitrophenyl ring, would exhibit a fa — Aromatic Hydrocarbons Chemistry Question

💡 Solution & Explanation

In $S_NAr$, the rate-determining step is the initial addition of the nucleophile, which is accelerated by strongly electronegative leaving groups that polarize the target carbon atom. The reactivity order for halogens is $F > Cl > Br > I$. The diazonium group ($-N_2^+$) is also an exceptionally excellent leaving group due to the formation of highly stable $N_2$ gas. Therefore, $F$, $Cl$, and $-N_2^+$ react faster than $Br$.