Understanding Alkoxide Attack on Primary Alkyl Halides

The question describes a specific type of organic reaction involving an alkoxide ion and a primary alkyl halide proceeding via an SN2 mechanism. Let's break down these components:

• SN2 Mechanism: This stands for Bimolecular Nucleophilic Substitution. It's a one-step reaction where a nucleophile attacks an electrophilic carbon atom, and the leaving group departs from that same carbon atom simultaneously. The reaction rate depends on the concentration of both the nucleophile and the substrate. SN2 reactions are favored by:
  • Uncrowded substrates (like primary alkyl halides).
  • Strong nucleophiles.
  • Aprotic polar solvents.
• Alkoxide Ion (RO⁻): This is the conjugate base of an alcohol. It acts as a strong nucleophile because it has a negative charge and the negative charge is localized on the oxygen atom, making it eager to attack electron-deficient centers.
• Primary Alkyl Halide (R'CH₂X): This is a molecule where a halogen atom (X) is attached to a primary carbon atom (a carbon atom bonded to only one other carbon atom). Primary alkyl halides have minimal steric hindrance around the carbon atom attached to the halogen, making them ideal substrates for SN2 reactions because the nucleophile can easily access the electrophilic carbon.

The Specific Reaction: Williamson Synthesis

When a strong nucleophile like an alkoxide ion (RO⁻) attacks a primary alkyl halide (R'CH₂X) through the SN2 mechanism, the nucleophile displaces the halide ion, forming an ether. This specific synthetic method is known as the Williamson synthesis.

The general reaction can be represented as:

$RO^- + R'CH_2X \rightarrow R'-O-R + X^-$

In this reaction:

• $RO^-$ is the alkoxide nucleophile.
• $R'CH_2X$ is the primary alkyl halide substrate.
• The nucleophilic oxygen atom of the alkoxide attacks the carbon atom bonded to the halogen.
• The C-X bond breaks, and the halide ion ($X^-$) leaves.
• A new C-O bond is formed, resulting in the ether product ($R'-O-R$).

Evaluating Other Synthesis Options

The other synthesis methods listed are fundamentally different:

• Arndt-Eistert synthesis: Used for homologation (increasing the carbon chain length by one) of carboxylic acids.
• Friedlaender synthesis: Used for synthesizing quinoline derivatives.
• Coumarin synthesis: Used for preparing coumarins, a class of organic compounds.

None of these involve the direct reaction of an alkoxide ion with a primary alkyl halide via SN2 to form an ether. Therefore, the reaction described in the question is distinctly the Williamson synthesis.