1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
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
phenol
-OH
1000
50-55
trace
45-50
toluene
-CH3
25
58
4
38
benzene
-H
1
N/A
iodobenzene
-I
0.2
2
60
chlorobenzene
-Cl
0.03
30
70
nitrobenzene
-NO2
0.00000006
6.4
93.3
0.3
trimethylammonium
-N+(Me)3
0.00000001
0
89
11
R
NO2
O2N
H(D)
C-D bond broken
C-H bond broken
+(D)H2O
+
NO+ 2
k-1
k1
k2