Dehydration of alcohols to ethers is catalysed by

Options

A. Conc. `H_(2)SO_(4)` at 413 K
B. Hot NaOH
C. hot HBr
D. hot `HNO_(3)`

Explanation

To solve the question "Dehydration of alcohols to ethers is catalyzed by," we need to analyze the options provided and understand the mechanism of dehydration of alcohols.

### Step-by-Step Solution:

1. **Understanding Dehydration of Alcohols**:
- Dehydration of alcohols involves the removal of a water molecule (H2O) from the alcohol to form an ether. This reaction typically requires a catalyst.

2. **Identifying the Catalyst**:
- Among the options provided, we need to identify which reagent can effectively catalyze the dehydration of alcohols to ethers.

3. **Analyzing the First Option: Concentrated H2SO4**:
- Concentrated sulfuric acid (H2SO4) is known to be a strong dehydrating agent.
- When alcohol (e.g., ethanol) is treated with concentrated H2SO4 at elevated temperatures (e.g., 413 K), it can protonate the alcohol, forming an oxonium ion.

4. **Mechanism of Reaction**:
- The mechanism involves:
- Protonation of the alcohol to form an oxonium ion.
- Elimination of water to form a carbocation.
- Nucleophilic attack by another alcohol molecule to form the ether.
- The final step involves deprotonation to yield the ether.

5. **Conclusion for the First Option**:
- Since concentrated H2SO4 facilitates the dehydration process and leads to the formation of ethers, this option is correct.

6. **Analyzing Other Options**:
- **Hot Sodium Hydroxide**: This is a strong base and does not catalyze dehydration but rather promotes elimination reactions. Therefore, this option is incorrect.
- **Other Acidic Options**: If there are other acidic options, they are also unlikely to catalyze the dehydration effectively compared to concentrated H2SO4.

7. **Final Answer**:
- The correct answer is that the dehydration of alcohols to ethers is catalyzed by **concentrated H2SO4 at 413 K**.