LSW S04
Exam 2
Reduction of Nitro Compounds:
NO2
[R]
Reaction type:
Reagents:
Limitations:
Benefits:
Aryl diazonium salts:
Reagents:
NH2
+
O N
O
H+
HO N
HNO2
+
H
H O N
O
H2O
255
O
LSW S04
Exam 2
Aryl Halides from Aryl Diazonium Salts:
CuCl
CuBr
N N
KI
HBF4
CuCN
H2O, Heat
N N
H2SO4
H3PO2
HO
OH
256
LSW S04
Exam 2
Aromatic Substitutions
Important reactions of aryl halides are:
1.
X
X
+
+
2.
X
+
ether
3.
X
+
+
257
H+
LSW S04
Exam 2
Aryl Grignards
X
Mg
+
ether
Halogens (X) are:
Halide reactivity:
Solvents:
258
XMg
LSW S04
Exam 2
Nucleophilic Aromatic Reactions:
Nu
X
-
Nu
+
+
Requirements:
Important events:


Timing determines mechanism
Addition-Elimination
Elimination-Addition
259
X-
LSW S04
Exam 2
Addition-Elimination Mechanism:
OMe
X
MeO
+
+
NO2
NO2
X
NO2
Reaction Kinetics:
Rate determining step:
N
O
N
N
O
O
Aryl halide reactivity:
260
O
O
LSW S04
Exam 2
Elimination-Addition Mechanism:
Elimination
H
H
X
H
H
NH2
+
H
H
H
H
H
Addition
H
H
H
H
H
NH2
H
H
+
H
H
H
H
H
Requirements:
H
H
Mg, THF H
heat
H
H
H
H
H
H
H
H
H
Benzyne Structure
H
H
Is benzyne an aromatic?

H
H

261

LSW S04
Exam 2
Addition Reactions of Benzyne
H
H
H
H
KNH2
H
NH3
H
KNH2
NH3
H
H
Cl
H
KOH
H2O
H
H
H2O
H
H
H
H
H
KNH2
NH3
H
+
H
H
H
H
CH3
H
H
H
CH3
H
H
H
H
CH3
CH3
Cl
KNH2
NH3
H
H
H
KNH2
NH3
H
H
H
H
H
KOH
H
H
H
H
H
H
H
H
H
H
H
H
H
KNH2
NH3
H
H
+
H
H
H
262
H
LSW S04
Exam 2
Diels-Alder Reactions of Benzyne:
H
H
H
H
+
H
H
H
H
O
NH2
CO2H
H
C O
O
Predict the product of the reaction of benzyne with:
(a) 1,3-butadiene
(b) furan
(c) H2O
(d) NH3
263
O