Question

Question #e1140

Answer 1

The third step in the Baeyer Villiger oxidation is the rate determining step because it involves the cleavage of a covalent bond.

Approximate rate constants for the steps are:

• Step 1 = `10^4` to `10^9 " L·mol"^-1"s"^(-1)`
• Step 2 = `10^10 " L·mol"^-1"s"^(-1)`
• Step 3 = `10^(-6)" s"^(-1)`
• Step 4 = `10^4` to `10^9 " L·mol"^-1"s"^(-1)`

Since no reaction can go faster than its slowest step, Step 3 is the rate determining step.

Step 1 is a simple OH proton transfer.

Such reactions are fast, with rate constants ranging from `10^4` to `10^9 "L·mol"^-6"s"^(-1)`.

Step 2 is the addition of an anion to a cation to form a neutral molecule.

These reactions are also very fast, with rate constants of about `10^10 "L·mol"^-6" s"^(-1)`

Step 3 is the decomposition of the acyl peroxide (the Criegee intermediate).

This involves the cleavage of a covalent O-O bond.

This is a much slower process. For example, the rate constant for the decomposition of t-butyl peroxyacetate is about `10^(-6)" s"^(-1)`.

Step 4 is another rapid proton transfer.