This document discusses the effect of substituent groups on the reactivity and substitution pattern of benzene. It notes that: - Reaction A with benzene is complete within 20-30 minutes, producing a single product. Reaction B with toluene is complete within 1 minute. Reaction C with nitrobenzene takes 2 hours, indicating substituents affect reaction rate. - Activating groups like alkyl, alkoxy and amino groups make the ring more electron-rich and reactive by resonance, directing substitution to the ortho and para positions. Deactivating groups like nitro, carboxyl and cyano make the ring electron-deficient and slower to react, directing to the meta position.

1. Effect of Substituent groups
on Benzene
Prof Dr Akkaladevi Muralidhar Rao
M.Pharm,PhD
St.Mary’s College Of Pharmacy
Secunderabad

2. H 2 SO 4
H 2 SO 4
CH 3
H 2 SO 4
NO 2
?
?
Can you guess ?
Which reaction is fast and why?
Possible products ?
Benzene
Nitro benzene
A
B
C

3. • Reaction A : Benzene reacts completely within
20 to 30 minutes and single product
• Reaction B: Toluene reacts within 1 minute
• Reaction C: Nitrobenzene reacts within 2
hours.

4. • elecrophilic substitution reactions -Typical
reactions of benzene
• What about alkenes?

6. • Ortho and para director
• Meta director

7. Effect of Group
• Any Group attached to a benzene ring affects
the reactivity of the ring
• Determines the orientation of the substitution
• Attack by electrophilic reagent -
how readily the attack occurs?
where it occurs ?

8. Activating group
(O and P directors)
Deactivating groups
(M directors)
CH3
OCH3
OH
NH2
Reaction is fast
Release electrons to the ring by
resonance and make it electron
rich
NO2
COOH
CN
Reaction is slow
Removes electrons from the ring
by resonance and make it
electron deficient

9. EXCEPTIONS
HALOGENS ARE DEACTIVATING GROUPS BUT
O & P DIRECTORS
F Cl Br I