Which of the following species have intra molecular H-bonds?

Options

A. Phenol
B. o-Nitrophenol
C. p-Nitrophenol
D. Nitroethane

Answer

To determine which species have intramolecular hydrogen bonds, we need to analyze the given compounds and identify the presence of hydrogen bonding within the same molecule. Let's break down the process step by step.

### Step-by-Step Solution:

1. **Understand Hydrogen Bonding**:
- Hydrogen bonding occurs when a hydrogen atom covalently bonded to a highly electronegative atom (like N, O, or F) interacts with another electronegative atom.
- Intramolecular hydrogen bonding happens within a single molecule, whereas intermolecular hydrogen bonding occurs between different molecules.

2. **Identify the Compounds**:
- The compounds mentioned are phenol, ortho-nitrophenol, para-nitrophenol, and nitromethane.

3. **Analyze Ortho-Nitrophenol**:
- Ortho-nitrophenol has an -OH group (hydroxyl) and a -NO2 group (nitro) in close proximity on the benzene ring.
- The -OH group can form a hydrogen bond with the oxygen of the -NO2 group within the same molecule, indicating the presence of intramolecular hydrogen bonding.

4. **Analyze Para-Nitrophenol**:
- In para-nitrophenol, the -OH and -NO2 groups are on opposite sides of the benzene ring.
- The distance between these two groups is too large for an intramolecular hydrogen bond to form, so this compound does not exhibit intramolecular hydrogen bonding.

5. **Analyze Phenol**:
- Phenol only contains the -OH group and does not have another electronegative atom nearby to form an intramolecular bond. Therefore, it does not have intramolecular hydrogen bonding.

6. **Analyze Nitromethane**:
- Nitromethane (C2H5NO2) does not have an -OH group. It has a nitro group and does not facilitate intramolecular hydrogen bonding as there is no hydrogen atom bonded to a highly electronegative atom within the same molecule.

7. **Conclusion**:
- The only compound that exhibits intramolecular hydrogen bonding is ortho-nitrophenol.

### Final Answer:
- The species that have intramolecular hydrogen bonds is **ortho-nitrophenol**.