Which alkenes give `CH_3CHO` on ozonolysis

Options

A. Hex-2-ene
B. But-2-ene
C. Propene
D. 1, 2-butadiene

Answer

To determine which alkenes yield CH₃CHO (acetaldehyde) upon ozonolysis, we can analyze each option step by step. Ozonolysis involves the cleavage of double bonds in alkenes using ozone (O₃), followed by reduction with zinc (Zn) and water (H₂O).

### Step-by-Step Solution:

1. **Understanding Ozonolysis**:
- Ozonolysis is a reaction where ozone reacts with alkenes to form carbonyl compounds (aldehydes or ketones).
- The general reaction involves the formation of ozonides, which are then hydrolyzed to yield carbonyl products.

2. **Analyzing Each Alkene**:
- We will analyze the given alkenes: H₂ene, but-2-ene, propene, and 1,2-butadiene.

3. **H₂ene**:
- Structure: H₂ene has a double bond at the second position.
- Upon ozonolysis, the double bond is cleaved, and we can form CH₃CHO (acetaldehyde) as one of the products.

4. **But-2-ene**:
- Structure: But-2-ene has a double bond between the second and third carbon atoms.
- Ozonolysis of but-2-ene also results in the formation of CH₃CHO.

5. **Propene**:
- Structure: Propene has a double bond between the first and second carbon atoms.
- Ozonolysis of propene leads to the formation of formaldehyde (HCHO) and another product, but not CH₃CHO.

6. **1,2-Butadiene**:
- Structure: 1,2-butadiene has double bonds between the first and second, and second and third carbon atoms.
- Ozonolysis of 1,2-butadiene results in the formation of CH₃CHO as one of the products.

### Conclusion:
From the analysis, the alkenes that yield CH₃CHO upon ozonolysis are:
- H₂ene
- But-2-ene
- 1,2-butadiene

**Final Answer**: H₂ene, but-2-ene, and 1,2-butadiene give CH₃CHO on ozonolysis.