9

General rule

•
•

EDG speed up reaction and direct to ortho and para positions
EWG slow down reaction and direct to meta positions.

Electronwithdrawing groups: Deactivating and meta-directing

using e.g. -N+R3 as substituent exerts a powerful electron withdrawing effect via
induction mechanism:

especially destabilising

leads to predominantly meta attack!

EWG:

Electron donating groups: Activating and ortho/para directing

(i)

weakly activating by inductive effect

especially stabilising; leads to ortho/para selectivity

EDG (weak):

NR3

H
E

NR3

H
E

NR3
H

E

NR3

NR3

NR3

H
E

H
E

H
E

NR3

NR3

NR3

H

E

H

E

H

E

o-attack

m-attack

p-attack

Me

H
E

Me

H
E

Me

H
E

Me

Me

Me

H
E

H
E

H
E

Me

Me

Me

H

E

H

E

H

E

o-attack

m-attack

p-attack

CF3

NO2

CF3

NO2

CF3

NO2

CF3
NO2
H

CF3

CF3

NO2
H

H

NO2

NO2
H

NO2