Ethers can be distinguished from alcohols by the following reaction :

Options

A. reaction with Na
B. reaction with `PCl_(5)`
C. reaction with 2,4-dinitrophenyl hydrazine
D. none of these

Explanation

To distinguish ethers from alcohols, we can analyze their reactions with sodium and phosphorus pentachloride (PCl5). Here’s a step-by-step solution to the question:

### Step 1: Reaction with Sodium
- **Alcohols**: When an alcohol (ROH) reacts with sodium (Na), it produces an alkoxide (RO⁻Na⁺) and hydrogen gas (H₂). The reaction can be represented as:
\[ \text{ROH} + \text{Na} \rightarrow \text{RO}^- \text{Na}^+ + \text{H}_2 \uparrow \]
This indicates that alcohols can react with sodium, leading to the evolution of hydrogen gas.

- **Ethers**: In contrast, when an ether (ROR) is treated with sodium, no significant reaction occurs. Therefore, ethers do not evolve hydrogen gas when treated with sodium.

### Step 2: Reaction with Phosphorus Pentachloride (PCl5)
- **Alcohols**: When an alcohol reacts with PCl5, it forms an alkyl chloride (RCl) along with phosphorus oxychloride (POCl3) and hydrochloric acid (HCl) as side products. The reaction can be summarized as:
\[ \text{ROH} + \text{PCl}_5 \rightarrow \text{RCl} + \text{POCl}_3 + \text{HCl} \]

- **Ethers**: When an ether reacts with PCl5, it can also yield alkyl chlorides, but in this case, two moles of alkyl chloride are formed along with POCl3. The reaction is represented as:
\[ \text{ROR} + \text{PCl}_5 \rightarrow 2 \text{RCl} + \text{POCl}_3 \]

### Step 3: Conclusion
From the reactions described:
- Alcohols react with sodium to produce hydrogen gas, while ethers do not.
- Both alcohols and ethers react with PCl5, but they produce different amounts of alkyl chlorides.

Thus, the best way to distinguish ethers from alcohols is by their reaction with sodium, where alcohols evolve hydrogen gas, and ethers do not.