Question

The trichloromethyl group is meta directing when attached to benzene ring due to 1)hyperconjugation

2)reverse hyperconjugation

3) +I effect

4) -I effect

Answer 1

The explanation for the correct option:

(2) Reverse Hyperconjugation (-H) effect

• The Reverse hyperconjugation is the donation of electron density from a filled $\pi$ orbital to a neighbouring ${\sigma }^{\ast }$ orbital.
• It is a destabilizing effect.
• In reverse hyperconjugation, the electron density flows in the opposite direction(from $\pi$ orbital to empty ${\sigma }^{\ast }$ orbital) than it does in the more common hyperconjugation from $\sigma$ orbital to empty p-orbital.
• The trichloromethyl group is meta directing when attached to benzene ring due to this reverse hyperconjugation due to the presence of electron withdrawing group, chloride ion.