Question

What is the action of ethane-1, 2 - diol on acetone?

Hint:

Cyclic acetals/ketals are used in organic synthesis as "protecting groups" for the carbonyl group because they are stable to bases.

Answer 1

Step 1: Understanding the Concept:
Ketones react with 1,2-diols in the presence of dry \(HCl\) gas to form stable cyclic products known as cyclic ketals.
Step 2: Detailed Explanation:
When acetone reacts with ethane-1,2-diol (ethylene glycol), a water molecule is eliminated.
The two hydroxyl groups of the glycol react with the carbonyl oxygen of the acetone.
Reaction:
\[ CH_3-CO-CH_3 + HO-CH_2-CH_2-OH \xrightarrow{\text{dry } HCl} \text{Acetone ethylene ketal} + H_2O \]
The product is a five-membered heterocyclic ring.
Step 3: Final Answer:
The reaction produces a cyclic ketal called acetone ethylene ketal.