How many structural isomer are possible for `C_4H_10O` (only alcohol).

Explanation

To determine how many structural isomers are possible for the molecular formula \( C_4H_{10}O \) (specifically alcohols), we need to identify the different ways we can arrange the carbon skeleton while ensuring that the functional group (the hydroxyl group, -OH) is included in each structure.

### Step-by-Step Solution:

1. **Identify the Molecular Formula**:
- The molecular formula given is \( C_4H_{10}O \). This indicates that we have 4 carbon atoms, 10 hydrogen atoms, and 1 oxygen atom.

2. **Determine the Type of Compound**:
- Since we are only considering alcohols, we will focus on the placement of the hydroxyl (-OH) group in the carbon skeleton.

3. **Draw the Carbon Skeletons**:
- The possible carbon skeletons for 4 carbon atoms can be linear (butane) or branched (isobutane).

4. **Identify the Isomers**:
- **1-Butanol**: The hydroxyl group is attached to the first carbon.
- Structure: \( CH_3-CH_2-CH_2-CH_2OH \)
- **2-Butanol**: The hydroxyl group is attached to the second carbon.
- Structure: \( CH_3-CH(OH)-CH_2-CH_3 \)
- **Isobutanol (2-Methyl-1-propanol)**: The hydroxyl group is attached to the first carbon of a branched chain.
- Structure: \( (CH_3)_2CH-CH_2OH \)
- **tert-Butanol (2-Methyl-2-propanol)**: The hydroxyl group is attached to the second carbon of a branched chain.
- Structure: \( (CH_3)_3C-OH \)

5. **Count the Isomers**:
- From the above structures, we can see that there are a total of 4 structural isomers for \( C_4H_{10}O \) when considering only alcohols.

### Final Answer:
There are **4 structural isomers** possible for \( C_4H_{10}O \) (only alcohols).

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