How many benzenoid isomers are possible for molecular formula `C_(7)H_(8)O` :-

Options

A. 3
B. 4
C. 5
D. 6

Answer

To determine the number of benzenoid isomers for the molecular formula C₇H₈O, we will follow a systematic approach.

### Step-by-Step Solution:

1. **Understanding the Molecular Formula**:
The molecular formula C₇H₈O indicates that we have 7 carbon atoms, 8 hydrogen atoms, and 1 oxygen atom. Since we are looking for benzenoid isomers, we know that these structures must contain at least one benzene ring (C₆H₅).

2. **Identifying the Benzene Ring**:
A benzene ring has the formula C₆H₆. In our case, we can think of the benzene ring as C₆H₅ when it is bonded to another group. This means we will have one benzene ring and we need to account for the remaining atoms from C₇H₈O.

3. **Calculating Remaining Atoms**:
After accounting for the benzene ring (C₆H₅), we have:
- 1 carbon (C) remaining (7 - 6 = 1)
- 3 hydrogens (H) remaining (8 - 5 = 3)
- 1 oxygen (O) remaining

4. **Possible Functional Groups**:
The remaining atoms can be arranged in different ways. The remaining carbon can be part of different functional groups:
- Methyl group (–CH₃)
- Hydroxymethyl group (–CH₂OH)

5. **Drawing Structures**:
We can now draw different structures based on the placement of the remaining carbon and the oxygen:
- **First Isomer**: Benzene with a methoxy group (–OCH₃).
- **Second Isomer**: Benzene with a hydroxymethyl group (–CH₂OH).
- **Third Isomer**: Benzene with a hydroxyl group (–OH) and a methyl group (–CH₃) at different positions.
- **Fourth Isomer**: Benzene with a methyl group (–CH₃) at one position and a hydroxyl group (–OH) at another position.
- **Fifth Isomer**: Benzene with a methyl group (–CH₃) and a hydroxymethyl group (–CH₂OH) at different positions.

6. **Counting the Isomers**:
After drawing and analyzing the structures, we find that there are a total of 5 distinct benzenoid isomers for the molecular formula C₇H₈O.

### Conclusion:
The total number of benzenoid isomers possible for the molecular formula C₇H₈O is **5**.

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