Sodium methoxide

Sodium methoxide is the simplest sodium alkoxide. With the formula CH₃ONa, it is a white solid, which is formed by the deprotonation of methanol. It is a widely used reagent in industry and the laboratory. It is also a dangerously caustic base.

Sodium methoxide

Names
IUPAC name Sodium methoxide
Other names Sodium methylate
Identifiers
CAS Number	124-41-4 Y
3D model (JSmol)	Interactive image
ChemSpider	29033 Y
ECHA InfoCard	100.004.273
PubChem CID	10942334
UNII	IG663U5EMC Y
CompTox Dashboard (EPA)	DTXSID8027030
InChI InChI=1S/CH3O.Na/c1-2;/h1H3;/q-1;+1 Y Key: WQDUMFSSJAZKTM-UHFFFAOYSA-N Y InChI=1/CH3O.Na/c1-2;/h1H3;/q-1;+1 Key: WQDUMFSSJAZKTM-UHFFFAOYAC
SMILES [Na+].[O-]C
Properties
Chemical formula	CH3NaO
Molar mass	54.02 g/mol
Appearance	White solid
Melting point	127 °C (261 °F; 400 K)
Boiling point	350 °C (662 °F; 623 K)[1] (decomposition)
Solubility in water	Reacts with water
Solubility	Soluble in ethanol, methanol Insoluble in hydrocarbons
Structure
Crystal structure	Hexagonal
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H251, H302, H314[2]
Precautionary statements	P235+P410, P280, P305+P351+P338, P310[2]
Safety data sheet (SDS)	Sigma[2]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Preparation and structure

Sodium methoxide is prepared by treating methanol with sodium:

2 Na + 2 CH₃OH → 2 CH₃ONa + H₂

The reaction is so exothermic that ignition is possible. The resulting solution, which is colorless, is often used as a source of sodium methoxide, but the pure material can be isolated by evaporation followed by heating to remove residual methanol.

As a solid, sodium methoxide is polymeric, with sheet-like arrays of Na⁺ centers, each bonded to four oxygen centers.^[3]

The structure, and hence the basicity, of sodium methoxide in solution depends on the solvent. It is a significantly stronger base in DMSO where it is more fully ionized and free of hydrogen bonding.^[4]

Applications

Organic synthesis

Sodium methoxide is a routinely used base in organic chemistry, applicable to the synthesis of numerous compounds ranging from pharmaceuticals to agrichemicals.^[4] As a base, it is employed in dehydrohalogenations and various condensations.^[5] It is also a nucleophile for the production of methyl ethers.^[6]

Industrial applications

Sodium methoxide is used as an initiator of anionic addition polymerization with ethylene oxide, forming a polyether with high molecular weight.^[7] Biodiesel is prepared from vegetable oils and animal fats (fatty acid triglycerides) by transesterification with methanol to give fatty acid methyl esters (FAMEs). Sodium methoxide acts as a catalyst for this reaction, but will combine with any free fatty acids present in the oil/fat feedstock to form soap byproducts.^{[citation needed]}

Stability

The solid hydrolyzes in water to give methanol and sodium hydroxide. Indeed, samples of sodium methoxide are often contaminated with sodium hydroxide, which is difficult to detect. The compound absorbs carbon dioxide from the air to form methanol and sodium carbonate, thus diminishing the alkalinity of the base.^{[citation needed]}

CH₃ONa + CO₂ + H₂O → 2 CH₃OH + Na₂CO₃

Commercial batches of sodium methoxide show variable levels of degradation, and were a major source of irreproducibility when used in Suzuki reactions.^[8]

Safety

Sodium methoxide is highly caustic and reacts with water to give methanol, which is toxic and volatile.

NFPA 704

The ratings for this substance vary widely.

Rating	3 4 3	3 4 2	3 3 2	3 2 2	2 2 2
Source	State of Connecticut[9]	DuPont[10]	Pharmco AAPR[11]	ScienceLab[12] (Both ratings on same sheet)

See also

• Methoxide
• Biodiesel production
• Sodium ethoxide