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330 CHAPTER 10 
 
 
 
 
10.11. 
(a) The mechanism for radical bromination of methane 
will have three distinct stages. The first stage is 
initiation, which creates bromine radicals. This initiation 
step involves homolytic bond cleavage (using Br2 and 
either heat or light) and should employ two fishhook 
arrows. 
 
 
 
The next stage involves propagation steps. There are two 
propagation steps: hydrogen abstraction to remove a 
hydrogen atom, followed by halogen abstraction to 
attach a bromine atom. Each of these steps should have 
three fishhook arrows. These two steps together 
represent the core reaction. They show how the product 
is formed. 
 
 
There are a number of possible termination steps to end 
the process. When drawing a mechanism for a radical 
reaction it is generally not necessary to draw all possible 
termination steps unless specifically asked to do so. It is 
sufficient to draw one termination step. Shown here is 
one termination step that also happens to produce the 
desired product. 
 
 
(b) During the bromination of methane, methyl radicals 
are produced. If two of these methyl radicals combine in 
a termination step, ethane is produced: 
 
 
 
 
10.12. 
(a) The tertiary position is expected to undergo selective 
bromination, giving the following alkyl bromide: 
 
 
 
(b) The tertiary position is expected to undergo selective 
bromination, giving the following alkyl bromide: 
 
 
 
(c) The tertiary position is expected to undergo selective 
bromination, giving the following alkyl bromide: 
 
 
 
10.13. The tertiary allylic position is expected to 
undergo selective bromination, giving the following 
alkyl bromide as the major product: 
 
O
O
O
O
OCH3
Br
Major 
 
Bromination at the benzylic position is also favorable 
because it proceeds via a resonance-stabilized, benzylic 
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