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-nitrophenols
D. o-nitrophenol is more volatile in steam than those of m- and p-isomer

Explanation

To understand why ortho-nitrophenol is less soluble in water than para- and meta-nitrophenols, we can break down the explanation into clear steps:

### Step-by-Step Solution:

1. **Identify the Compounds**:
- We have three isomers of nitrophenol: ortho-nitrophenol (o-NP), meta-nitrophenol (m-NP), and para-nitrophenol (p-NP).

2. **Understand Solubility in Water**:
- Solubility in water is largely determined by the ability of a compound to form hydrogen bonds with water molecules. The more hydrogen bonds a compound can form with water, the more soluble it is.

3. **Examine Ortho-Nitrophenol**:
- Ortho-nitrophenol has a hydroxyl (-OH) group and a nitro (-NO2) group that are positioned adjacent to each other on the benzene ring. This proximity allows for the formation of intramolecular hydrogen bonding within the molecule itself.

4. **Intramolecular Hydrogen Bonding**:
- In ortho-nitrophenol, the -OH group can form a hydrogen bond with the nitro group, which stabilizes the molecule internally. This intramolecular bonding reduces the availability of the -OH group to interact with water molecules.

5. **Compare with Meta and Para Isomers**:
- In contrast, meta-nitrophenol and para-nitrophenol do not have this intramolecular hydrogen bonding. Instead, they can form intermolecular hydrogen bonds with water, which enhances their solubility.

6. **Conclusion**:
- Since ortho-nitrophenol is involved in intramolecular hydrogen bonding, it is less capable of forming hydrogen bonds with water compared to para- and meta-nitrophenols. Therefore, ortho-nitrophenol is less soluble in water.

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

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