How will you convert the following compounds into benzene? (i) C2H4

Explanation

To convert ethene (C2H4) into benzene (C6H6), we can follow these steps:

### Step 1: Bromination of Ethene
- Ethene (C2H4) is treated with bromine (Br2) in a reaction known as bromination. This leads to the formation of 1,2-dibromoethane (C2H4Br2).

**Reaction:**
\[ C_2H_4 + Br_2 \rightarrow C_2H_4Br_2 \]

### Step 2: Dehydrohalogenation
- Next, we treat 1,2-dibromoethane with alcoholic potassium hydroxide (KOH). This reaction leads to the elimination of HBr and the formation of an alkene, specifically vinyl bromide (CH2=CHBr).

**Reaction:**
\[ C_2H_4Br_2 + KOH (alc) \rightarrow CH_2=CHBr + HBr \]

### Step 3: Formation of Acetylene
- The vinyl bromide (CH2=CHBr) is then treated with sodium amide (NaNH2), which results in the formation of acetylene (CH≡CH) through a dehydrohalogenation reaction.

**Reaction:**
\[ CH_2=CHBr + NaNH_2 \rightarrow CH \equiv CH + NaBr \]

### Step 4: Dimerization of Acetylene
- We need three moles of acetylene (CH≡CH) to form benzene. The acetylene molecules undergo cyclization when passed through a red-hot iron tube at a temperature of about 873 K.

**Reaction:**
\[ 3 CH \equiv CH \xrightarrow{873 K, Fe} C_6H_6 \]

### Final Product
- The final product of this reaction is benzene (C6H6).

### Summary of Steps:
1. Bromination of ethene to form 1,2-dibromoethane.
2. Dehydrohalogenation to form vinyl bromide.
3. Formation of acetylene from vinyl bromide.
4. Dimerization of acetylene to form benzene.

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