The Williamson ether synthesis is an SN2 reaction

The Williamson ether synthesis uses a base and an alkyl halide to convert an alcohol into a symmetrical or an unsymmetrical ether. The base deprotonates the alcohol to form an alkoxide that undergoes a nucleophilic substitution (SN2) reaction with the alkyl halide, producing the ether and a metal halide.  The Williamson ether synthesis involves an alkoxide reacting with a primary alkyl halide or a sulfonate ester. 

• Reagents: Base, Solvent (DMSO, DMF, etc.)
• Reactant: Aliphatic/Aromatic Alcohol and Alkyl, Allyl or Benzyl Halide
• Product: Ether
• Type of Reaction: S_N2
• Bond Formation: R₁-O-R₂

Lab Tips

• Dialkyl ethers are easily synthesized with a strong base such as NaH, KH, LHMDS, or LDA. Aryl ethers are synthesized with NaOH, KOH, K₂CO₃, or Cs₂CO₃.
• Use of dipolar aprotic solvents minimizes dehydrohalogenation side products.
• Tertiary or sterically hindered primary or secondary alkyl halides are prone to E2 elimination, affording an alkene product.
• Diaryl ethers cannot be prepared from phenoxides with unactivated aryl halides. The presence of copper metal or a Cu(I)-salt catalyst can make this reaction go (Ullmann biaryl ether synthesis), or if the aryl halide is activated with a strongly electron-withdrawing substituent.
• Alkali phenoxides may undergo C-alkylation in addition to O-alkylation.

_{Kürti, L., Czakó, B. (2005). Strategic Applications of Named Reactions in Organic Synthesis; Background and Detailed Mechanisms. Burlington, MA: Elsevier Academic Press.}

Mechanism

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