# What is oxidative cleavage?

Jan 23, 2016

Oxidative cleavage is the cleavage of carbon-carbon bonds to generate carbon-oxygen bonds. Sometimes $\text{C"-"C}$ bonds are oxidized, and sometimes $\text{C"-"C}$ and $\text{C"-"H}$ are oxidized.

OXIDATIVE CLEAVAGE: PERIODIC ACID

In general, an oxidative cleavage of a vicinal diol (commonly with periodic acid---pronounced "per-iodic") looks like this:

Notice how the $\text{C"-"C}$ bond is cleaved, and the resultant alcohol is oxidized one step forward (e.g. primary alcohol $\to$ aldehyde $\cancel{\to}$ carboxylic acid, using periodic acid).

PERIODIC ACID OXIDATIVE CLEAVAGE MECHANISM

The mechanism goes as follows (ignore the red iodine; the valency ought to be fine):

You don't have to know the mechanism, but I think it helps to have some idea on what happens "behind the scenes".

OXIDATIVE CLEAVAGE: OZONE (ALKENE)

On the other hand, an oxidative cleavage of an alkene using ozone looks like this:

For the first step, notice how in essence, the $\text{C"="C}$ bond was "transformed" into a $\text{C"="O}$ bond, and split into two carbonyl compounds. What follows depends on the type of workup reaction you perform on step 2.

REDUCTIVE WORKUP

For the second step, adding $\text{Zn}$, or adding ("CH"_3)_2"S", performs a "reductive workup", which ultimately gives you a "transformed" $\text{C"="C}$ bond and stops at the aldehyde or ketone.

OXIDATIVE WORKUP

For the second step, adding ${\text{H"_2"O}}_{2}$, a strong oxidizing agent for an "oxidative workup", ultimately gives you a "transformed" $\text{C"="C}$ bond as well as an oxidized $\text{C"-"H}$ bond.

Instead of stopping at the aldehyde or ketone, you go all the way to a carboxylic acid or ketone.

OZONE OXIDATIVE CLEAVAGE MECHANISM (ALKENE)

The general mechanism for oxidative cleavage of an alkene using ozone is:

OXIDATIVE CLEAVAGE: OZONE (ALKYNE)

For an alkyne:

OZONE OXIDATIVE CLEAVAGE MECHANISM (ALKYNE)

You don't have to know either mechanism, but I think it helps to have some idea on what happens "behind the scenes".