10

ii)

moderately and strongly activating via resonance

especially stabilising
leads to rate enhancement and ortho/para selectivity

electronegative heteroatom (i.e. electron withdrawing by inductive effect) BUT
possess electron pair available for resonance stabilisation. This leads to extra
canonical forms for ortho and para attack but notfor meta!

extra resonance form inherently more stable and thus greatly outweighs -I effect

EDG (moderate and strong):

Halobenzenes

Deactivating but ortho/para directing.

powerful inductive effect renders ring electron deficient and thus deactivated, but
ortho and para positions are less destabilised due to contributions from canonical
forms:

no such resonance stabilisation can be achieved for meta attack.

2.3.

Sulphonation

General reaction scheme:

OMe

H
E

OMe
H

E

OMe
H

E

OMe

OMe

OMe

H
E

H
E

H
E

OMe

OMe

OMe

H

E

H

E

H

E

OMe

H

E

OMe
H
E

o-attack

m-attack

p-attack

NH2

NR2

OH

OR

NHCOR

OCOR

Cl

H

E

Cl

H
E

R

R

SO3H

H2SO4

+

H2O

CF3

4.5 (-6)

67 (-6)
4.5 (-6)

dito

1

1

1

1

1

1

dito