1. 12.12 Substituent Effects in Electrophilic Aromatic Substitution: Activating Substituents8

2. Very strongly activating Strongly activating Activating
Table 12.2
Classification of Substituents in Electrophilic Aromatic Substitution Reactions
Very strongly activating
Strongly activating
Activating
Standard of comparison is H
Deactivating
Strongly deactivating
Very strongly deactivating 1

3. 1. All activating substituents are ortho-para directors.
Generalizations
1. All activating substituents are ortho-para directors.
2. Halogen substituents are slightly deactivating but ortho-para directing.
3. Strongly deactivating substituents are meta directors. 23

4. Electron-Releasing Groups (ERGs)
are ortho-para directing and activating
ERG
ERGs include —R, —Ar, and —C=C 25

5. Electron-Releasing Groups (ERGs)
are ortho-para directing and strongly activating
ERG
ERGs such as —OH, and —OR are strongly activating 25

6. occurs about 1000 times faster than nitration of benzene
Nitration of Phenol
occurs about 1000 times faster than nitration of benzene OH OH
NO2 OH
NO2
HNO3 +
44%
56% 26

7. Bromination of Anisole
FeBr3 catalyst not necessary
OCH3
OCH3 Br
Br2
acetic acid
90% 26

8. Oxygen Lone Pair Stabilizes Intermediate
OCH3 •• • H Br +
OCH3 •• • •• H Br +
OCH3 + H H H H H Br
all atoms have octets 26

9. Electron-Releasing Groups (ERGs)•
ERG
ERGs with a lone pair on the atom directly attached to the ring are ortho-para directing and strongly activating 25

10. Examples O OH OR OCR ERG = NHCR O NH2 NHR NR2•• OR • ••
OCR • ••
ERG = • •
NHCR • O •
NH2 •
NHR •
NR2
All of these are ortho-para directing and strongly to very strongly activating 25

11. Lone Pair Stabilizes Intermediates for ortho and para SubstitutionX +
ERG H X +
ERG
comparable stabilization not possible for intermediate leading to meta substitution 26

12. 12.13 Substituent Effects in Electrophilic Aromatic Substitution: Strongly Deactivating Substituents8

13. ERGs Stabilize Intermediates for ortho and para SubstitutionX +
ERG • H X +
ERG • 26

14. —CF3 is a powerful EWG. It is strongly deactivating and meta directing
Electron-withdrawing Groups (EWGs) Destabilize Intermediates for ortho and para Substitution
EWG
EWG X H H H + + H H H H H H X H
—CF3 is a powerful EWG. It is strongly deactivating and meta directing 26

15. Many EWGs Have a Carbonyl Group Attached Directly to the Ring
—CR
—EWG = O
—COH O
—COR O
—CCl
All of these are meta directing and strongly deactivating 25

16. All of these are meta directing and strongly deactivating
Other EWGs Include:
—EWG =
—NO2
—SO3H —C N
All of these are meta directing and strongly deactivating 25

17. Nitration of BenzaldehydeCH O
O2N CH O
HNO3
H2SO4
75-84% 26

18. Problem 12.14(a); page 468 Cl
CCl O
CCl O
Cl2
FeCl3
62% 26

19. Disulfonation of Benzene
HO3S
SO3
SO3H
H2SO4
90% 26

20. Bromination of NitrobenzeneFe
60-75% 26

21. F, Cl, Br, and I are ortho-para directing, but deactivating
12.14 Substituent Effects in Electrophilic Aromatic Substitution: Halogens
F, Cl, Br, and I are ortho-para directing, but deactivating 8

22. Nitration of ChlorobenzeneCl
NO2 Cl
NO2 Cl
NO2 Cl
HNO3 + +
H2SO4
30% 1%
69%
The rate of nitration of chlorobenzene is about 30 times slower than that of benzene. 6

23. Nitration of Toluene vs. Chlorobenzene42
2.5 58 Cl
0.029
0.029
0.009
0.009
0.137 15