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Consider the following bromination:
a. Calculate
b. Draw out a stepwise mechanism for the reaction, including the initiation, propagation, and termination steps.
c. Calculate
d. Draw an energy diagram for the propagation steps.
e. Draw the structure of the transition state of each propagation step.
(a)
Interpretation: The value of
Concept introduction: The value of
Answer to Problem 15.53P
The value of
Explanation of Solution
The given bromination reaction is,
In the given reaction,
The value of
Where,
•
•
The bond dissociation energy of
The bond dissociation energy of
The bond dissociation energy of
The bond dissociation energy of
Substitute the bond dissociation energy of
Therefore, the value of
The value of
(b)
Interpretation: The stepwise mechanism for the given reaction which includes initiation, propagation and termination steps is to be drawn.
Concept introduction: The general steps followed by free-radical reaction are stated below:
1. First step is initiation that involves formation of radical.
2. Second step is propagation.
3. Third step is the termination that involves the formation of stable bond.
Answer to Problem 15.53P
The stepwise mechanism for the given reaction which includes initiation, propagation and termination steps is,
Figure 1
Explanation of Solution
The initiation step involves the generation of bromine radical by hemolytic cleavage of
Figure 1
The stepwise mechanism for the given reaction which includes initiation, propagation and termination steps is shown in Figure 1.
(c)
Interpretation: The value of
Concept introduction: The general steps followed by free-radical reaction are stated below:
1. First step is initiation that involves formation of radical.
2. Second step is propagation.
3. Third step is the termination that involves the formation of stable bond.
Answer to Problem 15.53P
The value of
Explanation of Solution
The propagation step of given reaction involves two steps. In the first step
The value of
Where,
•
•
The bond dissociation energy of
The bond dissociation energy of
The bond dissociation energy of
The bond dissociation energy of
The value of
The value of
The value of
(d)
Interpretation: The energy level diagram for the propagation steps is to be drawn.
Concept introduction: The graphical representation of chemical reaction in which x-axis represents energy of the reaction and y-axis represents the reaction coordinate is called energy profile diagram.
Answer to Problem 15.53P
The energy level diagram for the propagation steps is,
Figure 2
Explanation of Solution
The energy level diagram for the propagation steps is shown in Figure 2.
Figure 2
The energy level diagram for the propagation steps is shown in Figure 2.
(e)
Interpretation: The structure of transition state of each propagation step is to be drawn.
Concept introduction: The general steps followed by free-radical reaction are stated below:
1. First step is initiation that involves formation of radical.
2. Second step is propagation.
3. Third step is the termination that involves the formation of stable bond.
Answer to Problem 15.53P
The structure of transition state of first and second propagation step is,
Figure 3
Explanation of Solution
The propagation step of given reaction involves two steps. In the first step
The transition state of the first propagation step is,
Figure 4
The transition state of the first propagation step is,
Figure 5
The structure of transition state of first and second propagation step is shown in Figure 4 and Figure 5, respectively.
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Chapter 15 Solutions
Organic Chemistry
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