Significations et usages de Sodium_methoxide

Sodium methoxide
IUPAC name sodium methoxide
Other names sodium methylate
Identifiers
CAS number	124-41-4 Y
PubChem	10942334
ChemSpider	29033 Y
UNII	IG663U5EMC Y
Jmol-3D images	Image 1
SMILES [Na+].[O-]C
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
Properties
Molecular formula	CH3NaO
Molar mass	54.02
Appearance	white solid
Melting point	127 ºC
Boiling point	>300 °C
Solubility	soluble in ethanol, methanol, fats, esters insoluble in hydrocarbons
Structure
Crystal structure	hexagonal
Hazards
MSDS	Oxford MSDS
EU classification	Harmful (Xn), Corrosive (C)
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Sodium methoxide is a chemical compound, with formula CH₃ONa. This colourless solid, which is formed by the deprotonation of methanol, is a widely used reagent in industry and the laboratory. It is also a dangerously caustic base.

  Preparation and structure

Sodium methoxide is prepared by carefully 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. The solid hydrolyzes in water to give sodium hydroxide, and commercial samples can be contaminated with the hydroxide. The solid and especially solutions absorb carbon dioxide from the air, thus diminishing the effectiveness of the base.

In the solid form, sodium methoxide is polymeric, with a sheet-like arrays of Na⁺ centers, each bonded to four oxygen centers.^[1]

The structure, and hence its basicity, of sodium methoxide in solution depends on the solvent. It is significantly stronger base in DMSO where it is more fully ionized and free of hydrogen bonding.^[2]

  Applications

  Organic synthesis

Sodium methoxide is a routine base in organic chemistry, applicable to the synthesis of numerous compounds, ranging from pharmaceuticals to agrichemicals.^[2] As a base, it is employed in dehydrohalogenations and various condensations.^[3] It is also a nucleophile for the production of methyl ethers.^[4]

  Industrial applications

Sodium methoxide is used as an initiator of anionic addition polymerization with ethylene oxide, forming a polyether with high molecular weight. Biodiesel is prepared from vegetable oils and animal fats, that is, fatty acid triglycerides, by transesterification with methanol to give fatty acid methyl esters (FAMEs). This transformation is catalyzed by sodium methoxide.

  Safety

Sodium methoxide is highly caustic, and the hydrolysis gives methanol, which is toxic and volatile.

  References

1. ^ E. Weiss, “Die Kristallstruktur des Natriummethylats” Zeitschrift fur Anorganische und Allgemeine Chemie 1964, volume 332, p. 197-203. doi:10.1002/zaac.19643320311
2. ^ ^{a b} Y. El-Kattan, J. McAtee, B. Bessieres “Sodium Methoxide” in Encyclopedia of Reagents for Organic Synthesis, John Wiley & Sons, 2006, New York. doi:10.1002/047084289X.rs089m.pub2. Article Online Posting Date: September 15, 2006.
3. ^ Omer E. Curtis, Jr., Joseph M. Sandri, Richard E. Crocker, Harold Hart (1963), "dicyclopropyl ketone", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv4p0278 ; Coll. Vol. 4: 278 
4. ^ Frederic Reverdin (1941), "3,5-Dinitroanisole", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv1p0219 ; Coll. Vol. 1: 219 

  See also

• Alkoxide
• Methoxide
• Biodiesel production
• Sodium ethoxide