Nucleophilic Aromatic Substitution

Vocabulary flashcards covering the mechanism, key intermediates, leaving groups, and structural requirements for nucleophilic aromatic substitution reactions.

Anionic $\sigma$-complex

The negatively charged intermediate formed during nucleophilic aromatic substitution following the attack of the nucleophile ($:Nu^-$) on the carbon bearing the leaving group ($X$).

Leaving groups in nucleophilic aromatic substitution

Halogens ($F$, $Cl$, $Br$) that depart from the aromatic ring to complete the substitution reaction.

Strong electron-withdrawing groups (STRONG EWG)

Substituents such as $NO_2$, $CN$, and $SO_2R$ that are required to activate the aromatic ring for nucleophilic aromatic substitution.

Positional requirement for EWG activation in $S_NAr$

The leaving group ($F$, $Cl$, $Br$) must be situated either ortho or para to a strong electron-withdrawing group ($NO_2$, $CN$, $SO_2R$).

Heteroaromatic positional requirement in $S_NAr$

The leaving group ($F$, $Cl$, $Br$) must be located directly next to the $N$ atom in a heteroaromatic ring (such as pyridine).