Williamson's synthesis of preparing dimethyl ether is a/an

Options

A. electrophilie substitution
B. `S_(N)1` reaction
C. electrophilic addition
D. `S_(N)2` reaction

Explanation

**Step-by-Step Text Solution:**

1. **Understanding Williamson's Synthesis**: Williamson's synthesis is a method for preparing ethers from alcohols and alkyl halides. In this case, we are focusing on the preparation of dimethyl ether.

2. **Reactants Identification**: For the synthesis of dimethyl ether (CH3-O-CH3), we need two main reactants:
- An alcohol: Methanol (CH3OH)
- An alkyl halide: Methyl chloride (CH3Cl)

3. **Formation of Alkoxide Ion**: The first step involves the deprotonation of methanol (the alcohol) using sodium (Na) to form the alkoxide ion:
\[ CH3OH + Na \rightarrow CH3O^{-}Na^{+} \]
Here, sodium donates an electron to the hydroxyl group, resulting in the formation of the alkoxide ion (CH3O^-).

4. **Nucleophilic Substitution Reaction**: The alkoxide ion (nucleophile) then attacks the methyl halide (CH3Cl) in a nucleophilic substitution reaction. The chlorine atom in methyl chloride is a good leaving group due to its electronegativity, creating a partial positive charge on the carbon atom:
\[ CH3O^{-} + CH3Cl \rightarrow CH3O-CH3 + Cl^{-} \]
This reaction involves the nucleophile attacking the electrophilic carbon in methyl chloride, leading to the formation of dimethyl ether and the release of chloride ion.

5. **Mechanism of Reaction**: The mechanism of this reaction is classified as an SN2 (bimolecular nucleophilic substitution) mechanism. In this mechanism, the nucleophile attacks the electrophile from the opposite side of the leaving group, resulting in a concerted reaction where bond formation and bond breaking occur simultaneously.

6. **Conclusion**: Therefore, Williamson's synthesis of dimethyl ether is an example of an SN2 mechanism.

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