Ozonolysis of which of the following alkene gives 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, yields propan-2-one (acetone) and methanal (formaldehyde).

1. **Explanation for Option 3 (2-Methyl Propene):**
   - The structure of 2-methyl propene is 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 the double bond in 2-methyl propene results in the formation of two fragments: one fragment is a ketone (propan-2-one) and the other is an aldehyde (methanal).
   - Specifically, the carbon atom bonded to two methyl groups becomes part of the ketone (propan-2-one), while the terminal carbon atom becomes methanal.
   - This matches the products given in the question, confirming that 2-methyl propene is the correct alkene.

2. **Explanation for why other options are incorrect:**

- **Option 1 (Propene):**
     - Propene (CH3-CH=CH2) upon ozonolysis would yield two molecules of methanal and one molecule of ethanal, not propan-2-one and methanal. Therefore, it does not match the required products.

- **Option 2 (But-1-ene):**
     - But-1-ene (CH3-CH2-CH=CH2) would produce ethanal and methanal upon ozonolysis. This does not match the required products of propan-2-one and methanal.

- **Option 4 (But-2-ene):**
     - But-2-ene (CH3-CH=CH-CH3) would yield two molecules of propan-2-one upon ozonolysis. This does not match the required products, as methanal is not formed.

In conclusion, the only alkene that produces the specified products, propan-2-one and methanal, upon ozonolysis is 2-methyl propene, making Option 3 the correct choice.