NaOCH3

Sodium methoxide, with the chemical formula NaOCH3 (often written CH3ONa), is the sodium salt of methanol. It is a white to off-white solid that is highly hygroscopic and rapidly absorbs moisture and CO2 from air. It can also be encountered as a methanolic solution, which is a common medium for its use in synthesis. In solid form, it is soluble in alcohols and in many organic solvents.

Preparation and handling

Sodium methoxide is typically prepared by reacting sodium metal with methanol: 2 CH3OH + 2 Na → 2 CH3ONa + H2. Dry, cold storage under inert atmosphere is recommended because it hydrolyzes in the presence of water to yield sodium hydroxide and methanol. It can also be formed in situ by deprotonating methanol with a strong base. Because of its moisture sensitivity, it is usually handled under strictly controlled humidity or as a methanolic solution.

Reactivity and uses

NaOCH3 is a strong base and a good nucleophile. It is widely used in organic synthesis for deprotonation of alcohols to form alkoxides and for nucleophilic substitutions. In the Williamson ether synthesis, sodium methoxide reacts with primary alkyl halides to give methyl ethers: R–X + CH3ONa → R–OCH3. It also serves as a catalyst and reagent in transesterification processes, notably the production of biodiesel from fats and methanol. On exposure to CO2, it slowly converts to sodium methyl carbonate; on contact with water, it hydrolyzes to NaOH and CH3OH.

Safety

Sodium methoxide is caustic and reacts violently with water, releasing heat and methanol. It should be handled with appropriate PPE, stored dry, and kept away from moisture, acids, and CO2. It is incompatible with air exposure and moisture-rich environments.