Chem 242
Spring 2008
Problem Set 5
Question 1. Predict the major product of the following reactions.
O
O
Me
Me
Br2, FeBr3
a)
Br
OH
O
Br
1) NaOH,
b)
2) H2 (1 atm), Pt catalyst
OH
Cl
1) HNO3, H2SO4
c)
Me
Me
NO2
2) NaOH
O
O
Me
Me
d)
Me
Me
SO3, H2SO4
SO3H
Chem 242
Spring 2008
Question 2. Provide reagents that will accomplish the following transformations.
Multiple steps may be needed.
1) acetyl chloride, AlCl3
a)
2) SO3/H2SO4
H3C
SO3H
O
NH2
NO2
Br
Br
1) H2 (1 atm), Pd catalyst
b)
2) Br2 (no FeCl3 needed)
Br
Me
O
Me
Me
1) isobutyryl chloride, AlCl3
c)
2) Cl2, FeCl3
Cl
Me
Me
Me
Me
OH
1) NaOH, Et–I
d)
2) t-butyl chloride, AlCl3
OEt
Chem 242
Spring 2008
Question 3. A student wanted to synthesize para-nitroaniline by nitration of aniline as
shown below.
NH2
NH2
HNO3, H2SO4
+ some ortho-product
NO2
a)
Provide a mechanism for the formation of para-nitroaniline.
O
O
N
N
O
O
H2SO4
O
OH
NH2
NH2
N
OH2
O
NH2
NH2
NH2
O
N
O2N
H
O2N
O
HSO4
H
O2 N
H
O2 N
H
NH2
NO2
b)
When the experiment was actually attempted, the reaction was very sluggish and
the product mixture contained large amounts of meta-nitroaniline. Briefly
explain the sluggish rate and the formation of meta-nitroaniline.
In strong acid, the amine will become protonated. An –NH3+ group is stongly deactivating and meta-directing.
NH2
fast reaction,
ortho/para products
NH3
slow reaction,
meta-products
HNO3, H2SO4
<.001%
>99.999%
Chem 242
Spring 2008
Question 4. When styrene is treated with aqueous sulfuric acid, one of the major
products is shown below. Provide a mechanism for this dimerization reaction.
Me
catalytic H+
protonate olefin
H+
Me
Me
benzene ring attacks
carbocation
(Friedel-Crafts rxn)
2nd olefin attacks
carbocation
Me
HSO4
H
elimination
Me
Chem 242
Spring 2008
Question 5. Provide a complete mechanism for the reaction shown below.
Me
AlBr3
Me
Me
Me
Me
Br
AlBr3
Me
Me
Br
AlBr3
ionization
& hydride
shift
Me
Me
Me
H
electrophilic attack (FriedelCrafts alkylation)
Br–
Me
Me
Me
Me
Me
H Me
Chem 242
Spring 2008
Question 6. Non-benzene aromatic compounds frequently show analogous reactivity to
benzene. With this in mind, explain why the bromination of furan occurs at the observed
position on the five-membered ring.
O
Br2, FeBr3
O
O
Br
Br
furan
product
O
not formed
O
Only 2 resonance
forms, less stable
H
O
"
Br+
" Br+ "
Br
Br
H
"
O
H
Br
Br
O
H
Br
Three resonance forms, more stable
O
product
Br
O
H
Br