One mole of an organic compound is found to require only `0.5 mol` of oxygen to produce an acid. Which class of compounds does the starting material belong to ?

Options

A. Alcohol
B. Aldehyde
C. Ether
D. Ketone

Explanation

To determine the class of the organic compound that requires only 0.5 moles of oxygen to produce an acid, we can analyze the oxidation reactions of different organic compounds.

### Step-by-Step Solution:

1. **Understanding the Reaction**:
We start with one mole of an organic compound and find that it requires only 0.5 moles of oxygen to produce an acid. The general reaction can be represented as:
\[ \text{Organic Compound} + 0.5 \, \text{O}_2 \rightarrow \text{Acid} \]

2. **Identifying Possible Classes of Compounds**:
The common classes of organic compounds that can be oxidized to form acids include:
- Alcohols
- Aldehydes
- Ethers
- Ketones

3. **Analyzing Each Class**:
- **Alcohols (RCOH)**:
Alcohols require at least 1 mole of oxygen to be oxidized to acids. Therefore, they cannot be the starting material since only 0.5 moles of oxygen are required.
\[ \text{RCOH} + \text{O}_2 \rightarrow \text{RCOOH} \quad (\text{requires } 1 \, \text{mol O}_2) \]
- **Aldehydes (RCHO)**:
Aldehydes can be oxidized to acids with only 0.5 moles of oxygen. The reaction can be represented as:
\[ \text{RCHO} + 0.5 \, \text{O}_2 \rightarrow \text{RCOOH} \]
This reaction is valid and shows that aldehydes can be converted to acids with the given amount of oxygen.
- **Ethers (R-O-R')**:
Ethers do not undergo oxidation to form acids. Therefore, they cannot be the starting material.
- **Ketones (RCOR')**:
Ketones also require at least 1 mole of oxygen to be oxidized to acids. Thus, they are not the starting material.
\[ \text{RCOR'} + \text{O}_2 \rightarrow \text{RCOOH} \quad (\text{requires } 1 \, \text{mol O}_2) \]

4. **Conclusion**:
Based on the analysis, the only class of compounds that can be oxidized to an acid using only 0.5 moles of oxygen is **aldehydes**.

### Final Answer:
The starting material belongs to the class of **aldehydes**.