Which of the following catalyst is used in the polymerisation of `CH-=CH` to `C_6H_6`

Options

A. `AlCl_3`
B. `HgSO_4`
C. `NbCl_3`
D. `HCl`

Explanation

To determine the catalyst used in the polymerization of ethyne (acetylene, CH≡CH) to form benzene (C6H6), let's follow these steps:

### Step 1: Understand the Reaction
Ethyne (CH≡CH) can undergo polymerization to form larger hydrocarbons. In this case, we are interested in the formation of benzene (C6H6).

### Step 2: Identify the Type of Reaction
The polymerization of ethyne to form benzene involves cyclization, where multiple ethyne molecules combine to form a cyclic structure. This is not a simple addition reaction but involves rearrangement and the formation of a stable aromatic compound.

### Step 3: Determine the Catalyst
The polymerization of ethyne to benzene typically requires a catalyst to facilitate the reaction. Common catalysts for such reactions include transition metals.

### Step 4: Common Catalysts
For the conversion of acetylene to benzene, catalysts such as:
- Nickel (Ni)
- Palladium (Pd)
- Platinum (Pt)

are often used. Among these, nickel is a widely used catalyst for this type of reaction.

### Step 5: Conclusion
Based on the above analysis, the catalyst used in the polymerization of CH≡CH to C6H6 is **Nickel (Ni)**.

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