How would you convert the following compounds into benzene?
(i) Ethyne
(ii) Ethene
(iii) Hexane

Explanation

To convert the given compounds into benzene, we can follow these steps:

### (i) Conversion of Ethyne to Benzene
1. **Starting Material**: Take 3 moles of ethyne (C₂H₂).
2. **Reaction Conditions**: Pass the ethyne through a red-hot iron tube.
3. **Reaction Type**: A polymerization reaction occurs where the ethyne molecules combine to form benzene (C₆H₆).
4. **Final Product**: The result is benzene.

### (ii) Conversion of Ethene to Benzene
1. **Starting Material**: Begin with ethene (C₂H₄).
2. **First Step**: Convert ethene to ethyne.
- **Reagents**: Add bromine (Br₂) in the presence of carbon tetrachloride (CCl₄) to the ethene. This adds bromine across the double bond.
- **Second Step**: Remove the bromine using alcoholic KOH, which acts as a dehydrohalogenating agent, resulting in the formation of ethyne.
3. **Next Step**: Use the ethyne obtained from the previous step.
4. **Final Step**: Pass the ethyne through a red-hot iron tube to convert it into benzene.

### (iii) Conversion of Hexane to Benzene
1. **Starting Material**: Take hexane (C₆H₁₄).
2. **First Step**: Cyclization of hexane.
- **Reagents**: Pass hexane over chromium oxide (CrO₃) or aluminum oxide (Al₂O₃) in the presence of molybdenum oxide (MoO₃).
- **Result**: This process leads to the formation of cyclohexane (C₆H₁₂).
3. **Next Step**: Convert cyclohexane to benzene.
- **Process**: Remove three hydrogen atoms from cyclohexane.
4. **Final Product**: The result is benzene.

### Summary of Conversions
- Ethyne → Benzene: 3 moles of ethyne → red-hot iron tube → Benzene.
- Ethene → Ethyne → Benzene: Ethene + Br₂ → Ethyne → red-hot iron tube → Benzene.
- Hexane → Cyclohexane → Benzene: Hexane → CrO₃/Al₂O₃/MoO₃ → Cyclohexane → remove H → Benzene.

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