Which of the following has highest boiling point ?

Options

A. Benzene,
B. Phenol
C. Toluene
D. Ethylbenzene

Answer

To determine which of the given compounds has the highest boiling point, we need to analyze the intermolecular forces present in each compound. The boiling point of a substance is influenced by the strength of these intermolecular forces; stronger forces lead to higher boiling points.

### Step 1: Identify the Compounds
The compounds mentioned are:
1. Benzene
2. Toluene
3. Ethyl benzene
4. Phenol

### Step 2: Analyze Intermolecular Forces
- **Benzene**: This compound has weak van der Waals forces (London dispersion forces) due to its non-polar nature.
- **Toluene**: Similar to benzene, toluene also exhibits weak van der Waals forces, but it has a slightly higher boiling point than benzene due to its larger size and polarizability.
- **Ethyl Benzene**: Ethyl benzene has similar weak van der Waals forces as benzene and toluene but is larger, thus it has a higher boiling point than both benzene and toluene.
- **Phenol**: Phenol, on the other hand, has strong hydrogen bonding due to the presence of the hydroxyl (-OH) group. Hydrogen bonds are significantly stronger than van der Waals forces.

### Step 3: Compare Boiling Points
- The boiling points of benzene, toluene, and ethyl benzene are relatively low due to weak van der Waals forces.
- Phenol, with its strong hydrogen bonding, will have a much higher boiling point compared to the other three compounds.

### Conclusion
Based on the analysis of intermolecular forces, **Phenol** has the highest boiling point among the given options.

### Final Answer
The compound with the highest boiling point is **Phenol**.

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