Ortho -nitrophenol is less soluble in water than `p`-and `m-`nitrophenols because

Options

A. o-nitrophenol shows intramolecular H-bonding
B. o-nitrophenol shows intermolecular H-bonding
C. melting point of o-nitrophenol is lower than those of m- and p-isomers
D. o-nitrophenol is more volatile in steam than those of m-and p-isomers .

Answer

To solve the question regarding the solubility of ortho-nitrophenol compared to para- and meta-nitrophenols, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Structures**:
- Draw the structures of ortho-nitrophenol, para-nitrophenol, and meta-nitrophenol.
- Ortho-nitrophenol has the -OH (hydroxyl) group and -NO2 (nitro) group adjacent to each other.
- Para-nitrophenol has these groups opposite each other.
- Meta-nitrophenol has the -NO2 group positioned one carbon away from the -OH group.

2. **Analyze Hydrogen Bonding**:
- In ortho-nitrophenol, the -OH group can form an intramolecular hydrogen bond with the -NO2 group. This means that the hydrogen from the -OH group is already involved in bonding with the nitro group and is not available to form hydrogen bonds with water.
- In contrast, para- and meta-nitrophenols do not have this intramolecular hydrogen bonding. Their -OH group can freely interact with water molecules, allowing for hydrogen bond formation.

3. **Evaluate Solubility**:
- The solubility of a compound in water is largely dependent on its ability to form hydrogen bonds with water.
- Since ortho-nitrophenol has its -OH group tied up in an intramolecular bond, it cannot form as many hydrogen bonds with water, leading to lower solubility.
- Para- and meta-nitrophenols, on the other hand, can form hydrogen bonds with water, which increases their solubility.

4. **Conclusion**:
- Therefore, the reason ortho-nitrophenol is less soluble in water than para- and meta-nitrophenols is due to the presence of intramolecular hydrogen bonding in ortho-nitrophenol, which reduces its ability to interact with water.

### Final Answer:
Ortho-nitrophenol is less soluble in water than para- and meta-nitrophenols because it forms intramolecular hydrogen bonds, which prevent it from forming hydrogen bonds with water.