Which of the following pairs of structures does not represent isomers?

Options

A.
B.
C.
D.

Answer

To determine which of the following pairs of structures does not represent isomers, we will analyze each option based on their molecular formulas and structural differences.

### Step-by-Step Solution:

1. **Identify the Molecular Formula**:
- For each pair of structures given in the options, write down the molecular formula for both compounds.

2. **Check for Isomerism**:
- **Isomers** are compounds that have the same molecular formula but different structural formulas.
- If two compounds have the same molecular formula but differ in their connectivity or functional groups, they are considered isomers.

3. **Analyze Each Option**:
- **Option 1**:
- Compound A: C5H6O
- Compound B: C5H6O
- The double bonds are in different positions (1 and 4 for A, 1 and 3 for B).
- Conclusion: These are positional isomers.

- **Option 2**:
- Compound A: C6H5O
- Compound B: C6H5O
- One is an alcohol, and the other is an ether.
- Conclusion: These are functional isomers.

- **Option 3**:
- Compound A: C6H6O
- Compound B: C6H6O
- One is an ether, and the other is a ketone.
- Conclusion: These are functional isomers.

- **Option 4**:
- Compound A: C5H6O
- Compound B: C5H6O
- Both compounds have the same structure (double bonds at positions 1 and 4).
- Conclusion: These are not isomers; they are identical compounds (homomers).

4. **Final Decision**:
- The pair of structures that does not represent isomers is **Option 4**.