Which of the following alcohols gives the best yield of dialkyl ether on being heated with a trace of sulphuric acid ?

Options

A. 2- pentanol
B. 2-Methly-2-butanol
C. 1-Pentanol
D. 2-Propanol

Explanation

To determine which alcohol gives the best yield of dialkyl ether when heated with a trace of sulfuric acid, we need to analyze the structure of the given alcohols and their ability to form carbocations.

### Step-by-Step Solution:

1. **Understanding the Reaction**:
- Alcohols can react with sulfuric acid to form dialkyl ethers through a nucleophilic substitution mechanism. In this process, the alcohol first forms a carbocation intermediate.

2. **Identifying the Alcohols**:
- The given alcohols are:
- 2-pentanol (secondary alcohol)
- 2-methyl-2-butanol (tertiary alcohol)
- 1-pentanol (primary alcohol)
- 2-propanol (secondary alcohol)

3. **Carbocation Stability**:
- The stability of carbocations is crucial for the reaction:
- Tertiary carbocations are the most stable.
- Secondary carbocations are less stable than tertiary but more stable than primary.
- Primary carbocations are the least stable.

4. **Analyzing Each Alcohol**:
- **2-pentanol**: Forms a secondary carbocation.
- **2-methyl-2-butanol**: Forms a tertiary carbocation.
- **1-pentanol**: Forms a primary carbocation.
- **2-propanol**: Forms a secondary carbocation.

5. **Best Yield for Dialkyl Ether**:
- For the formation of dialkyl ethers, a primary carbocation is preferred because it leads to a more favorable nucleophilic reaction.
- Among the options, **1-pentanol** is the only primary alcohol, which means it will produce a primary carbocation.

6. **Conclusion**:
- Therefore, **1-pentanol** will give the best yield of dialkyl ether when heated with a trace of sulfuric acid.

### Final Answer:
**1-pentanol** gives the best yield of dialkyl ether.