Chapter 25: Carbohydrates

Alkylation of Carbohydrates

Reaction type: Nucleophilic Substitution (S_N2)

Summary

• The -OH groups in carbohydrates react readily with alkylating agents to give ethers via a simple S_N2 reaction.
• Methylation can be achieved using methyl iodide, CH₃I, and silver oxide Ag₂O.
• Benzylation can be achieved using benzyl halides (Cl, Br, I), C₆H₅CH₂X and a base such as NaH or Ag₂O.
• These reactions are often used in carbohydrate chemistry since the products act as protecting groups for the reactive -OH functional group.
• The -OR group at the acetal center can be converted back to an -OH with aqueous acid.

Related Reactions

• Williamson ether synthesis
• Ether synthesis via Alcohol condensation
• Substitution Reactions of Alkyl Halides

© Dr. Ian Hunt, Department of Chemistry