Name: Nucleophilic Aromatic Substitution: Addition&amp;#8211;Elimination SNAr
Uploaded: 2023-04-30T10:33:09
Description: Learn by watching this video about Nucleophilic Aromatic Substitution: Addition–Elimination SNAr at JoVE.com

Recall that nucleophiles attack only those aryl halides that comprise strong electron-withdrawing substituents placed ortho or para to the leaving group.&#160;
The reaction proceeds via nucleophilic aromatic substitution, involving two steps&#8212;the addition of the nucleophile and the elimination of the leaving group.
In the first step, the nucleophile adds to the electron-deficient carbon that bears the leaving group. Subsequently, the electrons delocalize over the ring carbons.
Resonance interaction with the electron-withdrawing substituent allows it to temporarily take up the electron density.
The contributing resonance forms of the intermediates are termed Meisenheimer intermediates.
Among these, the structure that bears a negative charge on the oxygen atoms of the nitro group is particularly stable.
In the second step, the nitro group liberates the electrons into the ring to eliminate the leaving group and restore aromaticity.
To summarize, in ortho and para intermediates, the electrons are delocalized over the nitro group, while in meta, they are not.
As such, ortho and para isomers successfully undergo SNAr reactions, whereas, with meta isomers, the reaction does not occur.

nucleophilic aromatic substitution: addition&ndash;elimination (snar)

Nucleophilic substitution in aromatic compounds is feasible in substrates bearing strong electron-withdrawing substituents positioned ortho or para to the leaving group. The reaction proceeds via two steps: the addition of the nucleophile and the elimination of the leaving group.
The reaction begins&#160;with an attack of the nucleophile on the carbon that holds the leaving group. This results in the delocalization of the &#960; electrons over the ring carbons. The resonance interaction between the delocalized electron pair and the electron-withdrawing group further stabilizes the intermediate through the formation of Meisenheimer complexes. Finally, the electron-withdrawing group releases the electron back into the ring, facilitating&#160;the departure of the leaving group and restoring&#160;aromaticity.

Learn by watching this video about Nucleophilic Aromatic Substitution: Addition–Elimination SNAr at JoVE.com

Nucleophilic Aromatic Substitution: Addition&amp;#8211;Elimination SNAr

Nucleophilic Aromatic Substitution: Addition&ndash;Elimination (SNAr)

Nucleophilic substitution in aromatic compounds is feasible in substrates bearing strong electron-withdrawing substituents positioned ortho or para to the ...