The reagent that is used to convert phenol into benzene is:

Options

A. Zn dust
B. `CO_2`
C. `CHCl_2 // aq NaOH`
D. `Na_2 CrO_2 // H_2SO_4 `

Explanation

To convert phenol into benzene, we need to identify the appropriate reagent that facilitates this transformation. Here’s a step-by-step solution:

### Step 1: Identify the structure of phenol and benzene
- **Phenol** is an aromatic compound with a hydroxyl group (-OH) attached to a benzene ring.
- **Benzene** is a simple aromatic hydrocarbon with the formula C6H6, consisting of a six-carbon ring with alternating double bonds.

### Step 2: Understand the reaction type
- The conversion of phenol to benzene involves the removal of the hydroxyl group (-OH) from phenol. This process is known as reduction.

### Step 3: Identify suitable reagents for reduction
- Common reducing agents include metals like zinc, lithium aluminum hydride, and others. However, we need a reagent that specifically converts phenol to benzene.

### Step 4: Determine the correct reagent
- **Zinc dust** is a well-known reducing agent that can effectively remove the hydroxyl group from phenol, resulting in the formation of benzene.

### Step 5: Write the reaction
- The reaction can be represented as:
\[ \text{C}_6\text{H}_5\text{OH} + \text{Zn} \rightarrow \text{C}_6\text{H}_6 + \text{ZnO} \]
Here, phenol (C6H5OH) reacts with zinc (Zn) to produce benzene (C6H6) and zinc oxide (ZnO).

### Conclusion
- The reagent used to convert phenol into benzene is **zinc dust**.

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