Which of the following species will have intramolecular hydrogen bonding ?

Options

A.
B.
C.
D.

Answer

To determine which of the given species exhibits intramolecular hydrogen bonding, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding Intramolecular Hydrogen Bonding**:
- Intramolecular hydrogen bonding occurs when the hydrogen bond forms within a single molecule. This typically involves a hydrogen atom bonded to an electronegative atom (like oxygen or nitrogen) and another electronegative atom within the same molecule.

2. **Analyzing Option 1: Ortho-hydroxybenzaldehyde**:
- Structure: The molecule has a hydroxyl group (-OH) and a carbonyl group (C=O) in close proximity (ortho position).
- The hydrogen from the hydroxyl group can form a hydrogen bond with the oxygen of the carbonyl group.
- Conclusion: This molecule exhibits intramolecular hydrogen bonding.

3. **Analyzing Option 2: Meta-hydroxybenzoic acid**:
- Structure: The hydroxyl group is in the meta position relative to the carboxylic acid group (-COOH).
- The distance between the hydroxyl hydrogen and the carboxylic oxygen is too great for a hydrogen bond to form.
- Conclusion: This molecule does not exhibit intramolecular hydrogen bonding; it may show intermolecular hydrogen bonding.

4. **Analyzing Option 3: Para-nitrophenone**:
- Structure: The hydroxyl group is in the para position relative to the carbonyl group.
- Similar to option 2, the distance is too large for a hydrogen bond to form within the same molecule.
- Conclusion: This molecule does not exhibit intramolecular hydrogen bonding; it may show intermolecular hydrogen bonding.

5. **Analyzing Option 4: Ortho-chlorobenzaldehyde**:
- Structure: This molecule has a chlorine atom and a carbonyl group.
- Although the hydroxyl group is not present, the hydrogen bonding typically requires hydrogen to be bonded to electronegative atoms like O, N, or F. Chlorine is not favorable for hydrogen bonding.
- Conclusion: This molecule does not exhibit intramolecular hydrogen bonding.

### Final Conclusion:
- The only species that exhibits intramolecular hydrogen bonding is **Option 1: Ortho-hydroxybenzaldehyde**.