An alkene on ozonolysis yields only ethanal. There is an isomer of the alkene which on ozonolysis yields:

Options

A. a.Propanone and methanal
B. b.Propanone and ethanal
C. c.Ethanal and nethanal
D. d.Only propanone

Explanation

To solve the problem, we need to analyze the ozonolysis of an alkene that yields only ethanal (acetaldehyde) and then find an isomer of that alkene which, upon ozonolysis, yields different products.

### Step-by-Step Solution:

1. **Identify the Alkene**:
The alkene that yields only ethanal upon ozonolysis must be 1-butene (CH2=CH-CH2-CH3). The ozonolysis of 1-butene results in the cleavage of the double bond and the formation of ethanal (CH3CHO).

2. **Ozonolysis Reaction**:
The ozonolysis of 1-butene can be represented as follows:
\[ \text{CH}_2=\text{CH-CH}_2\text{-CH}_3 + \text{O}_3 \rightarrow \text{CH}_3\text{CHO} + \text{CH}_3\text{CHO} \]
This gives two molecules of ethanal.

3. **Identify Isomers**:
The isomers of 1-butene can be 2-butene (cis or trans). We will consider 2-butene for ozonolysis:
- **Cis-2-butene**: CH3-CH=CH-CH3
- **Trans-2-butene**: CH3-CH=CH-CH3

4. **Ozonolysis of 2-butene**:
Performing ozonolysis on 2-butene:
\[ \text{CH}_3-\text{CH}=\text{CH}-\text{CH}_3 + \text{O}_3 \rightarrow \text{CH}_3\text{COCH}_3 + \text{CH}_3\text{CHO} \]
This results in the formation of acetone (CH3COCH3) and ethanal (CH3CHO).

5. **Final Products**:
The ozonolysis of 2-butene yields acetone and ethanal. Thus, the isomer of the alkene that yields different products upon ozonolysis is 2-butene.

### Conclusion:
The isomer of the alkene that yields different products upon ozonolysis is 2-butene, which produces acetone and ethanal.