Which of the following cannot be made by using Williamson's synthesis?

Options

A. methoxybenzene
B. Benzyl p-nitrophenyl ether
C. tert-butyl methyl ether
D. di-tert-butyl ether

Explanation

To determine which of the given compounds cannot be synthesized using Williamson's synthesis, we need to analyze the steric hindrance associated with each compound. Williamson's synthesis involves the formation of ethers through an SN2 reaction, which is sensitive to steric hindrance.

### Step-by-Step Solution:

1. **Understanding Williamson's Synthesis**:
- Williamson's synthesis involves the reaction of an alcohol with sodium to form an alkoxide ion (RO⁻), which then reacts with an alkyl halide (R'-X) to form an ether (R-O-R').
- The reaction proceeds via an SN2 mechanism, which requires that the nucleophile (alkoxide ion) attacks the electrophile (alkyl halide) without significant steric hindrance.

2. **Analyzing the Given Compounds**:
- **Option A: Methoxybenzene (C6H5OCH3)**:
- The methoxy group is attached to a benzene ring, and the carbon attached to the oxygen has three hydrogen atoms. There is minimal steric hindrance, allowing for successful SN2 reaction.
- **Option B: Benzyl-P-nitrophenyl ether**:
- This compound has a benzyl group (C6H5CH2-) and a nitrophenyl group (C6H4NO2). The benzyl group is not sterically hindered, allowing for an SN2 reaction to occur.
- **Option C: Tert-butylmethyl ether (C(CH3)3OCH3)**:
- The tert-butyl group (C(CH3)3) is bulky, but it can still participate in the SN2 reaction with methyl halide (CH3Cl) due to the relatively low steric hindrance at the methyl position.
- **Option D: Di-tert-butyl ether (C(CH3)3OC(CH3)3)**:
- This compound has two bulky tert-butyl groups. When the alkoxide ion attempts to attack a methyl halide, the steric hindrance is significant, preventing the SN2 reaction from occurring. Instead, elimination may occur, leading to the formation of an alkene rather than an ether.

3. **Conclusion**:
- Among the options, **di-tert-butyl ether** (Option D) cannot be synthesized using Williamson's synthesis due to excessive steric hindrance, which prevents the necessary SN2 reaction from occurring.

### Final Answer:
**Option D: Di-tert-butyl ether cannot be made by using Williamson's synthesis.**