Which of the following pair of compounds is not functional isomers?

Options

A.
B.
C.
D.

Explanation

To determine which pair of compounds is not functional isomers, we need to understand the definition of functional isomers. Functional isomers are compounds that have the same molecular formula but different functional groups.

Let's analyze the options step by step:

### Step 1: Identify the pairs of compounds and their molecular formulas.

1. **Option A**: C4H10 and C4H10O
2. **Option B**: C4H8O and C4H8O
3. **Option C**: C3H6O and C3H6O
4. **Option D**: C3H6O2 and C3H6O2

### Step 2: Check the functional groups for each option.

- **Option A**:
- C4H10 could be an alkane (like butane).
- C4H10O could be an alcohol (like butanol) or an ether.
- Since the functional groups are different (alkane vs alcohol), this is a pair of functional isomers.

- **Option B**:
- Both compounds have the same molecular formula C4H8O.
- If we assume one is an alcohol and the other is a ketone, they have different functional groups. Thus, this is also a pair of functional isomers.

- **Option C**:
- Both compounds have the same molecular formula C3H6O.
- One could be an alcohol and the other a ketone, so they are functional isomers.

- **Option D**:
- Both compounds have the same molecular formula C3H6O2.
- If both are esters, they have the same functional group. Therefore, they are not functional isomers.

### Step 3: Conclusion

After analyzing all options, we find that:
- Options A, B, and C are functional isomers.
- Option D is not a pair of functional isomers because both compounds have the same functional group (ester).

Thus, the correct answer is **Option D**.

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