Intramolecular hydrogen bonding is present in

Options

A. water
B. o-nitrophenol
C. p-nitrophenol
D. methyl amine

Answer

To determine which compound exhibits intramolecular hydrogen bonding, we need to analyze the given options based on their molecular structures and the presence of functional groups that can participate in hydrogen bonding.

### Step-by-Step Solution:

1. **Understanding Intramolecular Hydrogen Bonding**:
- Intramolecular hydrogen bonding occurs within a single molecule, where a hydrogen atom is bonded to a highly electronegative atom (like N, O, or F) and interacts with another electronegative atom in the same molecule.

2. **Analyzing the Options**:
- **Option 1: Water (H2O)**:
- Water molecules can form hydrogen bonds with each other (intermolecular hydrogen bonding), but there is no intramolecular hydrogen bonding since it consists of separate molecules.
- **Conclusion**: Not intramolecular.

- **Option 2: Ortho-nitrophenol**:
- The structure of ortho-nitrophenol allows for the hydroxyl group (-OH) to form a hydrogen bond with the nitro group (-NO2) within the same molecule.
- **Conclusion**: This is an example of intramolecular hydrogen bonding.

- **Option 3: Para-nitrophenol**:
- In para-nitrophenol, the -OH and -NO2 groups are positioned far apart on the benzene ring, making intramolecular hydrogen bonding unlikely.
- **Conclusion**: Not intramolecular.

- **Option 4: Methyl amine (CH3NH2)**:
- Methyl amine can form hydrogen bonds with other methyl amine molecules (intermolecular hydrogen bonding), but there is no intramolecular hydrogen bonding present.
- **Conclusion**: Not intramolecular.

3. **Final Conclusion**:
- Based on the analysis, the compound that exhibits intramolecular hydrogen bonding is **Ortho-nitrophenol**.

### Answer:
**Ortho-nitrophenol** exhibits intramolecular hydrogen bonding.