Ethers can not be prepared by `:`

Options

A. Heating alkyl halide with dry silver oxide
B. Heating alkyl halide with ammonical KOH
C. Heating alkyl halide with pottasium alkoxide
D. Heating an excess of alcohol with alumina under pressure

Answer

To determine which method cannot be used to prepare ethers, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Option A: Heating alkyl halide with dry silver oxide (Ag2O)**
- Consider the alkyl halide, for example, ethyl bromide (C2H5Br).
- When ethyl bromide is heated with dry silver oxide, the reaction produces diethyl ether (C2H5OC2H5) and silver bromide (AgBr).
- **Conclusion**: This method can produce ethers.

2. **Option B: Heating alkyl halide with ammoniacal KOH**
- Again, using ethyl bromide (C2H5Br) as an example.
- When ethyl bromide is treated with ammoniacal KOH, it leads to the formation of diethyl ether (C2H5OC2H5) and potassium bromide (KBr).
- **Conclusion**: This method can also produce ethers.

3. **Option C: Heating alkyl halide with potassium alkoxide**
- Using ethyl bromide (C2H5Br) and potassium alkoxide (RO-K+), a reaction occurs.
- Instead of forming an ether, an elimination reaction (E2) takes place, resulting in the formation of an alkene (C2H4).
- **Conclusion**: This method cannot produce ethers.

4. **Option D: Heating an excess of alcohol with alumina under pressure**
- Consider ethanol (C2H5OH) as the alcohol.
- When ethanol is heated with alumina (Al2O3) under pressure, dehydration occurs, leading to the formation of diethyl ether (C2H5OC2H5).
- **Conclusion**: This method can produce ethers.

### Final Answer:
The method that cannot be used to prepare ethers is **Option C: Heating alkyl halide with potassium alkoxide**.

---