Sodium methoxide

Sodium methoxide is a chemical compound with the formula CH3ONa. This white 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.

Sodium methoxide
The sodium cation
Ball-and-stick model of the methoxide anion
Names
IUPAC name
Sodium methoxide
Other names
Sodium methylate
Identifiers
CAS Number
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.004.273
PubChem CID
UNII
CompTox Dashboard (EPA)
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
Safety data sheet Sigma[2]
GHS pictograms
GHS Signal word Danger
GHS hazard statements
 H251, H302, H314[2]
GHS precautionary statements
 P235+410, P280, P305+351+338, P310[2]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Preparation and structure

Sodium methoxide is prepared by treating methanol with sodium:

2 Na + 2 CH
3OH → 2 CH
3ONa + H
2

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 methanol and sodium hydroxide. Indeed, samples of sodium methoxide are often contaminated with sodium hydroxide. The compound absorbs carbon dioxide (and water vapor) from the air, thus diminishing the alkalinity of the base.

2 CH
3ONa + CO
2 + H
2O → 2 CH
3OH + Na
2CO
3

In the solid form, 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. 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 reacts with water to give methanol, which is toxic and volatile.

NFPA 704

The ratings for this substance vary widely.

Rating
4
3
3
4
3
2
3
3
2
2
3
2
2
2
2
Source State of Connecticut[7] DuPont[8] Pharmco AAPR[9] ScienceLab[10](Both ratings on same sheet)

See also

References
  1. Chandran, K.; Kamruddin, M.; Ajikumar, P.K.; Gopalan, A.; Ganesan, V. (2006). "Kinetics of thermal decomposition of sodium methoxide and ethoxide". Journal of Nuclear Materials. 358 (2–3): 111–128. doi:10.1016/j.jnucmat.2006.07.003. ISSN 0022-3115.
  2. Sigma-Aldrich Co., Sodium methoxide. Retrieved on 2018-05-24.
  3. E. Weiss (1964). "Die Kristallstruktur des Natriummethylats" [The Crystal Structure of Sodium Methylate]. Zeitschrift für Anorganische und Allgemeine Chemie (in German). 332 (3–4): 197–203. doi:10.1002/zaac.19643320311.
  4. Y. El-Kattan; J. McAtee; B. Bessieres (2006). "Sodium Methoxide". Encyclopedia of Reagents for Organic Synthesis. New York: John Wiley & Sons. doi:10.1002/047084289X.rs089m.pub2.
  5. O. E. Curtis, Jr., J. M. Sandri, R. E. Crocker, H. Hart (1958). "Dicyclopropyl ketone". Organic Syntheses. 38: 19. doi:10.15227/orgsyn.038.0019.CS1 maint: multiple names: authors list (link); Collective Volume, 4, p. 278
  6. F. Reverdin (1927). "3,5-Dinitroanisole". Organic Syntheses. 7: 28. doi:10.15227/orgsyn.007.0028.; Collective Volume, 1, p. 219
  7. "The Code Officials Perspective" (PDF).
  8. "DuPont Material Safety Data Sheet" (PDF).
  9. "Pharmco AAPR Material Safety Data Sheet" (PDF).
  10. "ScienceLab Material Safety Data Sheet".
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