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Sigma Complex. Intermediate is more stable if nitration occurs at the ortho or para position. =>. Energy Diagram. =>. =>. Activating, O -, P - Directing Substituents. Alkyl groups stabilize the sigma complex by induction , donating electron density through the sigma bond.

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sigma complex
Sigma Complex

Intermediate is more stable if nitration occurs at the orthoor para position.

=>

activating o p directing substituents

=>

Activating, O-, P-Directing Substituents

Alkyl groups stabilize the sigma complex by induction, donating electron density through the sigma bond.

Substituents with a lone pair of electrons stabilize the sigma complex by resonance.

nitration of anisole
Nitration of Anisole

Ortho attack

Meta attack

Para attack

=>

the amino group

=>

The Amino Group

Aniline reacts with bromine water (without a catalyst) to yield the tribromide. Sodium bicarbonate is added to neutralize the HBr that’s also formed.

deactivating meta directing substituents
Deactivating Meta-Directing Substituents

Electrophilic substitution reactions for nitrobenzene are 100,000 times slower than for benzene.

The product mix contains mostly the meta isomer, only small amounts of the orthoand para isomers.

Meta-directors deactivate all positions on the ring, but the meta position is less deactivated. =>