8

The nitration of benzene and hexadeutero benzene proceeds at the same rate,
although C-D bond is stronger than C-H bond.

This shows that C-H/C-D bond is NOTbroken in the rate determiningstep (r.d.s.).
Therefore the reaction must involve at least two steps.

k2>> k-1in both cases

2.2.1.Orientation and Reactivity

C6H5X

relative
rate

ortho

meta

para

IMAGE aromatics133.gif

phenol

-OH

1000

50-55

trace

45-50

toluene

-CH3

25

58

4

38

benzene

-H

1

N/A

N/A

N/A

iodobenzene

-I

0.2

38

2

60

chlorobenzene

-Cl

0.03

30

trace

70

nitrobenzene

-NO2

0.00000006

6.4

93.3

0.3

trimethylammonium

-N+(Me)3

0.00000001

0

89

11

IMAGE aromatics134.gif
IMAGE aromatics135.gif
IMAGE aromatics136.gif
IMAGE aromatics137.gif
IMAGE aromatics138.gif
IMAGE aromatics139.gif
IMAGE aromatics140.gif

R

NO2

R

O2N

H(D)

R

C-D bond broken

C-H bond broken

+(D)H2O

+

NO+
2

k-1

k1

k2

k-1

k2