Chemistry& 241
Clark College
Homework 8 SOLUTIONS
Please put your answers on a separate sheet of paper.
Due Tuesday, December 2nd, 2008, at the END OF CLASS.
1. Predict the products for the following reaction. If more than one product is likely to form, give all
products, and indicate which is/are major products, if applicable.
Br2
h!
*
Br
With Br, the reaction is extremely selective
for substitution at the 3° position, so this is
the only product that is formed.
NBS
h!
*
Br
Br
Br
Br
When doing a radical reaction with an allylic position, be sure to
generate every allylic radical and the corresponding resonance
structure! Each radical gets its own product. Also, each individual
molecule is a mixture of enantiomers, which is a racemic mixture.
racemic
Cl2
h!
Cl
Cl
Cl
Cl
Cl
minor
major
Homework 8
Fall 2008
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Chemistry& 241
Clark College
2. Give a detailed mechanism for the following reactions. Be sure to include all steps!
Initiation
Cl
Cl
Propagation
h! or !
Cl•
H
•Cl
H
Cl
Termination
2 Cl•
Cl
Cl
Cl
•Cl
•Cl
Cl
•Cl
Cl
Cl
H
(disproportionation optional)
Homework 8
Fall 2008
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Chemistry& 241
Clark College
Br
!
+ Br2
Br
With this reaction, no HBr is produced, so it is a bit different than the traditional reactions that we saw in
class. However, the steps and patterns remain the same! With this reaction, the easiest bond to break
is that highly strained (and highly straining) bridging bond. Rather than break a C-H bond, break the
C-C bond
Br
Initiation
Br
!
2 Br•
Br
Propagation
Br
Br
Br
Br
Br
Br
Br
Termination
Br•
Br
•Br
Br
Br
Br
Br•
Br
Br
Br
Br
Br
Br
Br
Br
Br
H
Homework 8
Fall 2008
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Chemistry& 241
Clark College
3. Give the six possible products (not including cis/trans isomers) for the following reaction:
O
N
O
!
Br
O
*
N
H
?
O
There are three different allylic positions on this molecule- each one generates
a radical and a resonance structure, for a maximum of 6 products.
*
*
Br
Br
Br
Br
Br
Br
4. An alkane with the molecular formula of C5H12 yields only one monochlorinated product when
heated with Cl2. What is the structure and IUPAC name of this molecule?
Cl2, !
Cl
Homework 8
2,2-dimethylpropane yields only one monochlorinated product.
Fall 2008
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