Question

How do you convert Acetylene to oxalic acid?

Answer 1

Hint: Here we are given acetylene which is an unsaturated hydrocarbon. Acetylene needs to be reacted with ozone and zinc dust to form glyoxal. Now glyoxal is reacted with alkaline potassium permanganate to form oxalic acid which has a carboxylic acid group attached to each other.

Complete answer:
Now in the above question we are being asked about the conversion of acetylene to oxalic acid.
First, we need to think of one single reaction which can convert acetylene to oxalic acid. There is no single reaction that can do that.
First let’s understand acetylene, it is an alkyne which is an unsaturated hydrocarbon. Now this unsaturated hydrocarbon is made to go under ozonolysis and then hydrolysis in the Presence of zinc dust. Now what zinc dust does is that it doesn’t let the chain break and still oxidises the compound. During the ozonolysis of acetylene, we have an intermediate called acetylene ozonide and it when hydrolysed in the Presence of zinc dust forms glyoxal.
Now glyoxal has two aldehyde functional group carbon attached to each other. The formula for glyoxal is $CHO - CHO$.
The above given compound now needs to be converted into oxalic acid which has the formula of $COOH - COOH$. Now to convert glyoxal to oxalic acid we need to oxidise glyoxal but not a strong oxidation because it might break the chain and form two compounds, therefore we will make it react with alkaline potassium permanganate which is an oxidising agent but a weak one.
On reaction of global with alkaline potassium permanganate we get oxalic acid.
Acetylene needs to be first reacted with ozone and zinc dust then the product we get needs to be reacted with alkaline potassium permanganate to get oxalic acid.

Note:
An absolute ozonolysis of any unsaturated hydrocarbon gives us two compounds out of the one product. The compound gets broken along its unsaturated hydrocarbon after forming an ozonide intermediate to give two aldehydes or carboxylic acid, depending on the unsaturated compound being alkene or alkyne.