o-nitrophenol is

Options

A. more volatile than p-nitrophenol
B. less volatile than p-nitrophenol
C. Equally volatile as p-nitrophenol
D. Non-volatile

Answer

To determine the volatility of ortho-nitrophenol compared to para-nitrophenol, we need to analyze the hydrogen bonding present in both compounds and how it affects their vapor pressures.

### Step-by-Step Solution:

1. **Understanding Volatility**:
- Volatility refers to how readily a substance can vaporize. A more volatile substance has a higher vapor pressure at a given temperature, meaning it can easily transition from liquid to gas.

**Hint**: Remember that volatility is linked to how easily a substance can form vapor.

2. **Identifying the Structures**:
- Ortho-nitrophenol has the nitro group (-NO2) positioned adjacent to the hydroxyl group (-OH) on the benzene ring.
- Para-nitrophenol has the nitro group positioned opposite to the hydroxyl group on the benzene ring.

**Hint**: Visualize the molecular structures to understand the spatial arrangement of functional groups.

3. **Analyzing Hydrogen Bonding**:
- In ortho-nitrophenol, intramolecular hydrogen bonding occurs. This means that the hydrogen bond forms within the same molecule, which can stabilize the structure but does not significantly hinder vaporization.
- In para-nitrophenol, intermolecular hydrogen bonding occurs. This means that hydrogen bonds form between different molecules, leading to stronger associations and a higher boiling point.

**Hint**: Differentiate between intramolecular (within the same molecule) and intermolecular (between different molecules) hydrogen bonding.

4. **Impact on Vaporization**:
- The presence of intramolecular hydrogen bonding in ortho-nitrophenol means that the bonds are weaker and can break more easily when heat is applied, allowing for easier vaporization.
- In contrast, the intermolecular hydrogen bonding in para-nitrophenol creates stronger associations between molecules, requiring more energy to break these bonds and vaporize the substance.

**Hint**: Consider how the strength of hydrogen bonds affects the energy required for vaporization.

5. **Conclusion**:
- Since ortho-nitrophenol has weaker intramolecular hydrogen bonds compared to the stronger intermolecular hydrogen bonds in para-nitrophenol, ortho-nitrophenol is more volatile than para-nitrophenol.

**Final Answer**: Ortho-nitrophenol is more volatile than para-nitrophenol.