UNIT 4 MECHANISMS
Mechanism 1 – Nucleophilic Addition
1.
Carbonyls with HCN and NaBH4 (H-):
a)
-
+

R1
CN
H
O
+

OH
H+
..O
C
R1
R2
R1
C
CN
R2
R2
:CN-
C
CN
b)
R1
H
O
+

H
O

OH
..O
C
C
R1
R2
R1
H
+
H
OH-
R2
R2
:H-
C
Mechanism 2 – Nucleophilic Addition-Elimination
2.
Acyl chlorides with water, ammonia, alcohols and primary amines:
a)
+
R
O
O-
-
C
R
C
Cl
..
O
H
H
O
Cl
R
+
O
H
-
C
O+
H
:Cl
H
O
R
H
+ HCl
C
O
H
b)
O
+
R
-
O
C
R
Cl
..
N
H
O-
H
Cl
C
R
+ HCl
C
R
+
N
N
H
H
H
H
H
H
H
O
-
C
+
N
H
:Cl
H
c)
O
+
R1
C
Cl
..
O
H
O-
R1
Cl
C
R1
C
+
O
O
H
R2
R2
H
R2
+ HCl
C
R1
+
O
R2
O
:Cl
O
d)
H
R2

+

R
O
C
1
Cl
..
N
H
N
..
H
O-
O
O
R1
C
Cl
R1
R1
C
+
N
+
N
R2
N
H
R2
H
R2
H
R2
H
3.
Mechanism 3 – Electrophilic Substitution
H
+ R2NH3Cl
C
H
Nitration, alkylation and acylation of benzene rings:
a)
H2SO4 + HNO3  H2NO3+ + HSO4H2NO3+  H2O + NO2+
HSO4
NO+2
H
+
NO2
NO2
+
H2SO4
R-Cl + AlCl3  R+ + AlCl4- (using a haloalkane)
or
b)
C
C
+
HCl
+
AlCl3
C
C+
+
AlCl4-
(using an alkene and HCl)
AlCl4
+
H
R
R
+
+
R
R-COCl + AlCl3  RCO+ + AlCl4-
c)
AlCl4
R
AlCl3
+
C
H
O
R
C
+
C
O
R
O
+
AlCl3