The reaction of 
 
follows the reaction coordinate diagram shown below.

a. Count the number of intermediate and transition states present.
b. Arrange the reaction species in order of increasing stability.
c. Which is more stable, the transition state between X and Y, or the transition state between Y and Z?
d. Which step has a higher rate constant in the forward direction? In the reverse direction?

• A. a. Intermediate: 2 ; Transition state: 1
  b. X < Y < Z
  c. transition state between X and Y
  d. forward: k1 ; reverse: k-1
• B. a. Intermediate: 1 ; Transition state: 2
  b. Y < Z < X
  c. transition state between Y and Z
  d. forward: k2 ; reverse: k-1
• C. a. Intermediate: 1 ; Transition state: 2
  b. X < Z < Y
  c. transition state between X and Y
  d. forward: k2 ; reverse: k-2
• D. a. Intermediate: 2 ; Transition state: 1
  b. Y > Z > X
  c. transition state between Y and Z
  d. forward: k-2 ; reverse: k1

Answer: (B)