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 need to understand the process of ozonolysis and the structures of the alkenes involved. Here’s a step-by-step solution:

### Step 1: Understand Ozonolysis
Ozonolysis is a reaction where alkenes react with ozone (O₃) to form ozonides, which can be further reduced to yield carbonyl compounds (aldehydes or ketones). The reaction cleaves the double bond of the alkene.

### Step 2: Identify the Structure of Acetaldehyde
Acetaldehyde has the molecular formula CH₃CHO. This indicates that it has a two-carbon chain with a carbonyl group (C=O) at one end.

### Step 3: Consider Possible Alkenes
To produce CH₃CHO through ozonolysis, we need to consider alkenes that, when cleaved, will yield this specific aldehyde.

1. **1-Butene (CH₂=CH-CH₂-CH₃)**:
- Ozonolysis of 1-butene results in:
- CH₃CHO (acetaldehyde) and CH₂=O (formaldehyde).

2. **2-Butene (CH₃-CH=CH-CH₃)**:
- Ozonolysis of 2-butene results in:
- CH₃CHO (acetaldehyde) and CH₃CHO (another acetaldehyde).

3. **1-Pentene (CH₂=CH-CH₂-CH₂-CH₃)**:
- Ozonolysis of 1-pentene results in:
- CH₃CHO (acetaldehyde) and CH₃-CH₂-CHO (propionaldehyde).

### Step 4: Conclusion
The alkenes that yield CH₃CHO upon ozonolysis include:
- 1-Butene
- 2-Butene
- 1-Pentene

### Summary of Alkenes:
- **1-Butene**: Produces CH₃CHO and CH₂O.
- **2-Butene**: Produces two equivalents of CH₃CHO.
- **1-Pentene**: Produces CH₃CHO and CH₃-CH₂CHO.