# Write a short note on oxidation of alcohols. What are the different reactions involved, with suitable examples?

Mar 20, 2016

The oxidation of alcohols requires having a proton on the same carbon as the hydroxyl group.

Do you see how there are two protons on a primary (${1}^{\circ}$) alcohol and one proton on a secondary (${2}^{\circ}$) alcohol that are attached to the same carbon as the one to which the $\text{OH}$ group is attached?

Also, notice that that proton is actually lost. You lose two hydrogens adjacent to each other (one of which is on the $\text{OH}$) and gain one $\text{C"-"O}$ bond during the oxidation.

In the case of an oxidation from the aldehyde to the carboxylic acid, you gain $\text{H"_2"O}$ and lose two hydrogens (one of which is on the same carbon as the $\text{OH}$ as expected), overall giving you one more oxygen.

As far as I know, it's not possible to lose a $\text{C"-"H}$ bond for oxidation of an alcohol, if it is not attached to the same carbon as the hydroxyl group. That means a tertiary (${3}^{\circ}$) alcohol cannot be oxidized to anything.

Examples of oxidation of alcohols are:

• ${\text{H"_2"CrO}}_{4}$ (chromic acid) to get a carboxylic acid from a primary alcohol, or a ketone from a secondary alcohol.
• ("CH"_3)_2"S"="O" and $\text{Cl"-("C"="O")_2"Cl}$ at $- {60}^{\circ} \text{C}$, and then work up with ${\text{Et"_3"NH}}_{2}$ (the Swern oxidation) to go from a primary alcohol to an aldehyde or a secondary alcohol to a ketone.
• $\text{PCC}$ in ${\text{CH"_2"Cl}}_{2}$ to get an aldehyde from a primary alcohol, but not a carboxylic acid.