Williamson synthesis of ether is an example of:

The Williamson synthesis of ether is a method used to prepare ethers. It involves the reaction between an alkoxide ion and an alkyl halide. Let me explain this step by step.

Consider the general reaction: an alkoxide ion, represented as $$ RO- $$, reacts with an alkyl halide, represented as $$ R'X $$, where R and R' are alkyl groups (which can be the same or different), and X is a halogen atom like chlorine, bromine, or iodine. The reaction produces an ether and a salt. The chemical equation is:

$$ RO- + R'X -> ROR' + X- $$

Now, let's analyze the mechanism. The alkoxide ion $$ RO- $$ has a negatively charged oxygen atom, making it electron-rich. This means it acts as a nucleophile (a species that donates an electron pair). The alkyl halide $$ R'X $$ has a polar carbon-halogen bond, where the carbon atom is partially positive (electrophilic) due to the higher electronegativity of the halogen. The nucleophile ($$ RO- $$) attacks the electrophilic carbon atom of the alkyl halide. This leads to the breaking of the carbon-halogen bond and the formation of a new carbon-oxygen bond. As a result, the halogen atom (X) is displaced as a halide ion.

This process involves the substitution of the halogen atom in the alkyl halide by the alkoxy group (OR). Since the attacking species is a nucleophile, and it replaces another group (the halide), this reaction is classified as a nucleophilic substitution reaction.

Now, comparing this with the given options:

Option A: Nucleophilic substitution - This matches the mechanism described above.

Option B: Electrophilic addition - This involves an electrophile adding to a double bond, which does not occur here as there is no unsaturated bond in the reactants.

Option C: Nucleophilic addition - This involves a nucleophile adding across a double bond, typically seen in carbonyl compounds, but here we have substitution, not addition.

Option D: Electrophilic substitution - This is common in aromatic compounds where an electrophile replaces a hydrogen atom, but Williamson synthesis involves aliphatic compounds and nucleophilic attack.

Therefore, Williamson synthesis is a nucleophilic substitution reaction.

Hence, the correct answer is Option A.