Name the alkene which on ozonolysis give acetone :

Question

Accepted Answer

To determine which alkene gives acetone upon ozonolysis, we need to understand the ozonolysis process. Ozonolysis is a reaction where ozone (O₃) cleaves the carbon-carbon double bonds in alkenes, resulting in the formation of carbonyl compounds (aldehydes or ketones).

Let's analyze each option:

1. **But-2-ene**: Ozonolysis of but-2-ene would result in the formation of two molecules of acetaldehyde (CH₃CHO), not acetone. This is because the double bond is between the second and third carbon atoms, leading to the cleavage that forms two identical aldehyde molecules.

2. **But-1-ene**: Ozonolysis of but-1-ene would yield propanal (CH₃CH₂CHO) and formaldehyde (HCHO). The double bond is between the first and second carbon atoms, leading to these products, neither of which is acetone.

3. **2,3-dimethyl but-2-ene**: This is the correct option. Ozonolysis of 2,3-dimethyl but-2-ene results in the formation of two molecules of acetone (CH₃COCH₃). The double bond is between the second and third carbon atoms, and the presence of methyl groups on both sides of the double bond ensures that the cleavage results in acetone, a ketone.

4. **Propene**: Ozonolysis of propene would produce acetaldehyde (CH₃CHO) and formaldehyde (HCHO). The double bond is between the first and second carbon atoms, leading to these products, neither of which is acetone.

In conclusion, only 2,3-dimethyl but-2-ene (Option 3) undergoes ozonolysis to produce acetone, due to its specific structure and the position of the double bond, which results in the formation of ketones rather than aldehydes. This is why Option 3 is the correct answer.