Kinetic analysis of the reaction R → V in the presence of a catalyst Cat yields the following information:
• The reaction energy profile has four distinct transition states.
• The first activation barrier is the largest, making the first step rate-determining.
• Two intermediates, I₁ and I₂, accumulate to detectable concentrations; no others are observed.
Four mechanisms are proposed:
(I) R → I₁ (slow)
I₁ → I₂ (fast)
I₂ → V (fast)
(II) R + Cat ⇌ RC (fast equilibrium)
RC → I₁ (slow)
I₁ → I₂ (fast)
I₂ + Cat → V + Cat (fast)
(III) R → I₁ (fast)
I₁ → I₂ (slow)
I₂ → V (fast)
(IV) R → I₁ (slow)
I₁ → I₂ (fast)
I₂ → I₃ (fast)
I₃ → V (fast)
Which proposed mechanism is most consistent with the experimental data?
a) Mechanism I
b) Mechanism II
c) Mechanism IV
d) Mechanism III