The intramolecular hydrogen bond is present in

Options

A. phenol
B. o - nitrophenol
C. p - nitrophenol
D. p - cresol

Answer

To determine which compound contains an intramolecular hydrogen bond, we need to analyze each option based on the conditions for hydrogen bonding. Here’s a step-by-step solution:

### Step 1: Understand the Conditions for Intramolecular Hydrogen Bonding
- An intramolecular hydrogen bond occurs when a hydrogen atom is covalently bonded to a highly electronegative atom (like O, N, or F) and is also close enough to another electronegative atom with a lone pair within the same molecule.

### Step 2: Analyze Each Option
1. **Phenol**:
- Structure: C6H5OH
- The hydrogen is attached to oxygen (OH), which is capable of forming a hydrogen bond. However, there is no other electronegative atom with a lone pair in the same molecule.
- **Conclusion**: No intramolecular hydrogen bond.

2. **Ortho-Nitrophenol**:
- Structure: C6H4(OH)(NO2) (where NO2 is at the ortho position relative to OH)
- The hydrogen in the OH group is capable of forming a hydrogen bond with the oxygen in the nitro group (NO2) because the nitro group has lone pairs.
- **Conclusion**: Intramolecular hydrogen bond is present.

3. **Para-Nitrophenol**:
- Structure: C6H4(OH)(NO2) (where NO2 is at the para position relative to OH)
- Although the nitro group has lone pairs, it is too far away from the OH group to form an intramolecular hydrogen bond.
- **Conclusion**: No intramolecular hydrogen bond.

4. **Paracresol**:
- Structure: C6H4(OH)(CH3) (where CH3 is at the para position relative to OH)
- The OH group is present, but there is no electronegative atom with a lone pair in the same molecule to form a hydrogen bond.
- **Conclusion**: No intramolecular hydrogen bond.

### Step 3: Final Conclusion
- The only compound that forms an intramolecular hydrogen bond is **Ortho-Nitrophenol**.

### Answer:
The intramolecular hydrogen bond is present in **Ortho-Nitrophenol**.

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