Chapter 6: Problem 6.45 (page 243)

Consider the following energy diagram for the conversion of $A \overset{}{\to G}$ .
a. Which points on the graph correspond to transition states?
b. Which points on the graph correspond to reactive intermediates?
c. How many steps are present in the reaction mechanism?
d. Label each step of the mechanism as endothermic or exothermic.
e. Label the overall reaction as endothermic or exothermic.

Short Answer

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Answer

Points B, D, and F are the transition states.
Points C and E are the reactive intermediates.
The reaction has three steps.
Step A-C is endothermic. While the steps C-E and E-G are exothermic.
The overall reaction is exothermic.

Step by step solution

Step-by-Step SolutionStep 1: Transition States

Transition State is a higher energy partial molecular state. The energy of the transition state is the minimum threshold energy that is required for the conversion of reactants to the products in concerted reactions.

The transition state cannot be isolated from the reaction medium.

Intermediates

The intermediates are highly unstable molecules that form in between the reaction pathway.

The intermediates can be isolated from the reaction mixture.

Explanation

Points B, D, and F are the transition states.
Points C and E are the reactive intermediates.
Since the reaction has three transition states, the reaction has three steps.
In step A-C, the energy of the intermediate C is higher. Hence, the reaction is endothermic. In steps C-E and E-G, the energy of the intermediates C and E are higher. Hence, the reactions in these steps are exothermic.
The overall reaction is exothermic.