Alkyl chloride is prepared by passing the …A… gas through solution of alcohol. Here, A refers to

Options

A. `H_(2)SO_(4)`
B. `Cl_(2)`
C. dry `HCl`
D. None of these

Explanation

To prepare alkyl chloride from alcohol, we need to identify the gas represented by "A" in the question. The process involves passing a specific gas through a solution of alcohol. Here’s the step-by-step solution:

### Step 1: Identify the Reaction
We need to prepare alkyl chloride (RCl) from an alcohol (R-OH). The common method for this conversion involves using a reagent that can provide the chloride ion (Cl⁻).

**Hint:** Think about common reagents used in organic chemistry for chlorination reactions.

### Step 2: Determine the Gas
The gas that is typically used for this reaction is dry hydrogen chloride (HCl). This gas can react with the alcohol to form the alkyl chloride.

**Hint:** Consider what gas would provide a chloride ion in the reaction.

### Step 3: Understand the Role of the Catalyst
In this reaction, zinc chloride (ZnCl₂) is often used as a catalyst. It helps facilitate the reaction between the alcohol and hydrogen chloride.

**Hint:** Remember that catalysts are substances that speed up reactions without being consumed in the process.

### Step 4: Reaction Mechanism
When dry HCl gas is passed through the alcohol solution in the presence of ZnCl₂, the following occurs:
1. The alcohol is protonated by H⁺ from HCl, making it a better leaving group.
2. The protonated alcohol forms a carbocation.
3. The chloride ion (Cl⁻) from HCl attacks the carbocation, resulting in the formation of the alkyl chloride.

**Hint:** Consider the steps involved in carbocation formation and nucleophilic attack.

### Conclusion
Thus, the gas "A" that is passed through the alcohol to prepare alkyl chloride is **dry HCl**.

**Final Answer:** A = dry HCl