Direction (Q. Nos. 19-20) Consider the following four compounds
(I) `CH_(3) - CH_(2) - CH_(2) - CH_(2) - overset(O)overset(||)(C) - H`
(II) `CH_(3) - CH_(2) - CH_(2) - overset(O)overset(||)(C) - CH_(3)`
(III) `CH_(3) - CH_(2) - underset(O)underset(||)(C) - CH_(2) - CH_(3)`
(IV) `CH_(3) - underset(CH_(3))underset(|)(CH) - CH_(2) - underset(O)underset(||)(C) - H`
Which of the following pairs are position isomers ?

Options

A. I and II
B. II and III
C. II and IV
D. III and IV

Explanation

To determine which pairs of the given compounds are position isomers, we first need to understand the definition of position isomers. Position isomers are compounds that have the same molecular formula and the same functional group but differ in the position of the functional group on the carbon chain.

### Step-by-Step Solution:

1. **Identify the Compounds**:
- (I) `CH₃ - CH₂ - CH₂ - CH₂ - C(=O) - H` (Aldehyde)
- (II) `CH₃ - CH₂ - CH₂ - C(=O) - CH₃` (Ketone)
- (III) `CH₃ - CH₂ - C(=O) - CH₂ - CH₃` (Ketone)
- (IV) `CH₃ - C(CH₃) - CH₂ - C(=O) - H` (Aldehyde)

2. **Count the Carbon Atoms**:
- All compounds need to have the same number of carbon atoms to be considered position isomers.
- Compounds (I), (II), (III), and (IV) all have 5 carbon atoms.

3. **Identify the Functional Groups**:
- (I) and (IV) are aldehydes.
- (II) and (III) are ketones.

4. **Check for Position Isomers**:
- **Compare (I) and (IV)**:
- (I) has the aldehyde group at the end of a 5-carbon chain.
- (IV) has the aldehyde group at the end of a branched 5-carbon chain.
- Since the carbon chain is not the same, they are not position isomers.
- **Compare (II) and (III)**:
- (II) has the ketone group on the second carbon of a 5-carbon chain.
- (III) has the ketone group on the third carbon of a 5-carbon chain.
- Since they have the same carbon chain and differ in the position of the ketone group, they are position isomers.

5. **Conclusion**:
- The only pair of compounds that are position isomers are (II) and (III).

### Final Answer:
The pairs that are position isomers are (II) and (III).