Ozonolysis of which of the following alkenes produces propan-2-one and methanal?

Question

Accepted Answer

Ozonolysis is a reaction where an alkene is cleaved by ozone to form carbonyl compounds. In this case, we are looking for an alkene that, upon ozonolysis, produces propan-2-one (acetone) and methanal (formaldehyde).

1. **Option 2: 2-Methyl propene**  
   2-Methyl propene has the structure CH3-C(CH3)=CH2. During ozonolysis, the double bond is cleaved, and each carbon atom involved in the double bond is converted into a carbonyl group. The cleavage of 2-methyl propene results in the formation of propan-2-one (acetone, CH3-CO-CH3) and methanal (formaldehyde, H-CHO). This matches the products specified in the question, confirming that Option 2 is correct.

2. **Option 1: Propene**  
   Propene has the structure CH3-CH=CH2. Ozonolysis of propene would yield two molecules of methanal (formaldehyde, H-CHO) and one molecule of ethanal (acetaldehyde, CH3-CHO), not propan-2-one and methanal. Therefore, Option 1 is incorrect.

3. **Option 3: 2-Methyl-1-butene**  
   2-Methyl-1-butene has the structure CH3-CH2-C(CH3)=CH2. Ozonolysis of this alkene would produce acetone (propan-2-one, CH3-CO-CH3) and propanal (CH3-CH2-CHO), not methanal. Thus, Option 3 is incorrect.

4. **Option 4: But-2-ene**  
   But-2-ene has the structure CH3-CH=CH-CH3. Ozonolysis of but-2-ene would yield two molecules of ethanal (acetaldehyde, CH3-CHO), not propan-2-one and methanal. Therefore, Option 4 is incorrect.

In conclusion, the only alkene that produces propan-2-one and methanal upon ozonolysis is 2-methyl propene, making Option 2 the correct choice.