In the reaction `Ar - OH +RX overset ("Alkali") to A ` . A is :

Options

A. An aldehyde
B. An aryl chloride
C. An ether
D. A ketone

Answer

To solve the question regarding the reaction of phenol with an alkyl halide in the presence of alkali, let's break down the steps involved in this reaction:

### Step-by-Step Solution:

1. **Identify the Reactants**:
- The reactants in this reaction are phenol (Ar-OH) and an alkyl halide (RX).

2. **Role of Alkali**:
- The alkali acts as a base. Bases are known to deprotonate acidic hydrogens. In phenol, the hydrogen atom of the hydroxyl (-OH) group is acidic.

3. **Formation of Phenoxide Ion**:
- When phenol reacts with the alkali, the base removes the acidic hydrogen from the hydroxyl group, resulting in the formation of a phenoxide ion (Ar-O⁻). This ion is a strong nucleophile.

4. **Nucleophilic Attack**:
- The phenoxide ion (Ar-O⁻) then acts as a nucleophile and attacks the electrophilic carbon in the alkyl halide (RX). The alkyl halide has a partial positive charge on the carbon atom (R) and a leaving group (X).

5. **SN2 Mechanism**:
- The reaction proceeds via an SN2 mechanism, where the nucleophile (phenoxide ion) attacks the electrophile (alkyl halide), leading to the displacement of the leaving group (X).

6. **Formation of Ether**:
- The result of this nucleophilic substitution is the formation of an ether. The product formed is an alkyl phenyl ether (Ar-O-R), where the alkyl group (R) is now bonded to the oxygen of the phenoxide ion.

7. **Conclusion**:
- Therefore, the final product A is an ether, specifically an alkyl phenyl ether.

### Final Answer:
A is an **ether**.