methoxide

Methoxide refers to the methoxide ion, CH3O−, and to its salts such as sodium methoxide (NaOCH3) and potassium methoxide (KOCH3). Methoxide is a strong base and nucleophile widely used in organic synthesis. In solution, especially in methanol, methoxide acts as a reactive reagent for deprotonation, transesterification, and nucleophilic substitution. The methoxide ion is the conjugate base of methanol and is highly reactive with moisture and carbon dioxide.

Preparation and handling

Methoxide salts are typically prepared by deprotonating methanol with reactive metals or hydride sources (for example, Na metal or NaH). They are commonly sold as dry solids or as solutions in methanol. Because they are highly hygroscopic and react with water and CO2, they are stored under inert atmosphere and dry conditions.

Reactions and applications

Methoxide serves as a versatile base in deprotonation steps and as a nucleophile in SN2 reactions. It is commonly used for transesterification, including the production of biodiesel from triglycerides by converting fats with methanol to methyl esters. In organic synthesis, methoxide can promote ether formation via Williamson ether synthesis, for example reacting with alkyl halides to generate methyl ethers or ethers derived from other alkyl groups. It also functions as an initiator or catalyst in certain anionic polymerizations.

Safety

Methoxide reagents are caustic and corrosive, irritant to skin and eyes, and react violently with water and acids. They should be handled with appropriate protective equipment, under dry, inert conditions, and kept away from moisture and acids. Contact with skin or eyes requires immediate rinsing and medical attention.

See also: sodium methoxide, potassium methoxide.