1. Substituent Effects - Induction
Inductive effect – movement of electron density through sigma bonds, based on electronegativity
Example – inductive effect on a carbocation
Cation Cation Stabilized Cation Destabilized
alkyl group donates electron density, stabilizes carbocation
-CF3 group removes electron density, destabilizes carbocation

2. Inductive Effects
Controlled by electronegativity and polarity of bonds in functional groups
Alkyl groups donate electrons by induction

3. Inductive Effects
Controlled by electronegativity and polarity of bonds in functional groups
Halogen (-X), -C=O, -CN, -CF3, -SO3H and -NO2 groups withdraw electrons inductively through sigma bonds.
(-OR and -NH2 groups also withdraw by induction)

4. Substituent Effects - Resonance
Resonance effect – movement of electrons through pi bonds, based on conjugation
Example – resonance effect donating electron density
Cation Cation Stabilized by Resonance
oxygen can donate electron density via resonance using its lone pairs

5. Resonance Effects – Electron Donation
Halogen, -OH, alkoxyl (-OR), and amino (-NH2) substituents donate electrons
electrons flow from substituents into the ring
Effect is greatest at ortho and para positions
any lone pair on atom next to ring can donate e- density by resonance

6. Substituent Effects - Resonance
Resonance effect – movement of electrons through pi bonds, based on conjugation
Example – resonance withdrawing electron density
Benzene Carbonyl Substituent
Which ring has more e- density?
Carbonyl group – gives the ring a partial plus charge

7. Resonance Effects – Electron Withdrawal
-C=O, -CN, -SO3H, and -NO2 substituents withdraw electrons from the aromatic ring by resonance
 electrons flow from the ring to the substituent
These aromatic rings all have less electron density than benzene itself due to the electron-withdrawing substituent.

8. Substituent Effects
Q. How do different substituents influence the rate of electrophilic aromatic substitution reactions? (activate or deactivate the ring)
Q. How do different substituents effect the orientation of the substitution reaction? (ortho/para vs. meta substitution)
Answer: Inductive Effects Resonance Effects x