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
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.004.273
UNII
  • InChI=1S/CH3O.Na/c1-2;/h1H3;/q-1;+1 checkY
    Key: WQDUMFSSJAZKTM-UHFFFAOYSA-N checkY
  • InChI=1/CH3O.Na/c1-2;/h1H3;/q-1;+1
    Key: WQDUMFSSJAZKTM-UHFFFAOYAC
  • [Na+].[O-]C
Properties
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)
Reacts with water
Solubility Soluble in ethanol, methanol
Insoluble in hydrocarbons
Structure
Hexagonal
Hazards
GHS labelling:
GHS02: FlammableGHS05: CorrosiveGHS07: Exclamation mark
Danger
H251, H302, H314[2]
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).
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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.

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.

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
NFPA 704 four-colored diamond
3
4
3
NFPA 704 four-colored diamond
3
4
2
NFPA 704 four-colored diamond
3
3
2
NFPA 704 four-colored diamond
3
2
2
NFPA 704 four-colored diamond
2
2
2
Source State of Connecticut[9] DuPont[10] Pharmco AAPR[11] ScienceLab[12] (Both ratings on same sheet)

See also

References
  1. Chandran, K.; Kamruddin, M.; Ajikumar, P.K.; et al. (2006). "Kinetics of thermal decomposition of sodium methoxide and ethoxide". Journal of Nuclear Materials. 358 (2–3): 111–128. Bibcode:2006JNuM..358..111C. doi:10.1016/j.jnucmat.2006.07.003. ISSN 0022-3115.
  2. Sigma-Aldrich Co., Sodium methoxide. Retrieved on 2022-03-21.
  3. Weiss, E. (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. El-Kattan, Y.; McAtee, J.; Bessieres, B. (2006). "Sodium Methoxide". Encyclopedia of Reagents for Organic Synthesis. New York: John Wiley & Sons. doi:10.1002/047084289X.rs089m.pub2. ISBN 0471936235.
  5. Curtis, O. E., Jr.; Sandri, J. M.; Crocker, R. E.; Hart, H. (1958). "Dicyclopropyl ketone". Organic Syntheses. 38: 19. doi:10.15227/orgsyn.038.0019.{{cite journal}}: CS1 maint: multiple names: authors list (link); Collective Volume, vol. 4, p. 278
  6. Reverdin, F. (1927). "3,5-Dinitroanisole". Organic Syntheses. 7: 28. doi:10.15227/orgsyn.007.0028.; Collective Volume, vol. 1, p. 219
  7. Bailey, Frederick E.; Koleske, Joseph V. (2000). "Polyoxyalkylenes". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a21_579. ISBN 3527306730.
  8. Wethman, Robert; Derosa, Joseph; Tran, Van; et al. (2020-08-19), An Under-Appreciated Source of Reproducibility Issues in Cross-Coupling: Solid-State Decomposition of Primary Sodium Alkoxides in Air, American Chemical Society, doi:10.26434/chemrxiv.12818234.v1, S2CID 242420220
  9. "Biodiesel: From the Field to the End User" (PDF). ct.gov. Office of Education and Data Management, State of Connecticut. 2008-04-08. Archived from the original on 2014-02-25. Retrieved 2022-01-29.{{cite web}}: CS1 maint: unfit URL (link)
  10. "Product Safety Summary Sheet DuPont™ Sodium Methoxide (Sodium Methylate)". DuPont. 2012-09-11. Retrieved 2022-01-29 – via nanopdf.com.
  11. "Pharmco AAPR Material Safety Data Sheet" (PDF). pharmcoaaper.com. Archived from the original (PDF) on 2014-02-23. Retrieved 2022-01-29.
  12. "ScienceLab Material Safety Data Sheet". Archived from the original on 2015-09-09. Retrieved 2022-01-29.
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