Sodium ethoxide
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| Names | |
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| IUPAC name
Sodium ethoxide
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| Other names
Sodium ethanolate, sodium ethylate (obsolete)
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| Identifiers | |
3D model (JSmol)
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| ChemSpider | |
| ECHA InfoCard | 100.004.989 |
PubChem CID
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CompTox Dashboard (EPA)
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| Properties | |
| C2H5ONa | |
| Molar mass | 68.05 g/mol |
| Appearance | white or yellowish powder hygroscopic |
| Density | 0.868 g/cm^3 (of a 21 wt% solution in ethanol) |
| Melting point | 260 °C (500 °F; 533 K) |
| Reacts | |
| Solubility | miscible with ethanol and methanol |
| Acidity (pKa) | 15.5[1] |
| Hazards | |
| NFPA 704 (fire diamond) | |
| Safety data sheet (SDS) | Oxford MSDS |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Sodium ethoxide (also is the organic compound with the formula C2H5ONa) is a white to yellowish powder that dissolves in polar solvents such as ethanol. It is commonly used as a strong base.[2]
Preparation
Few procedures have been reported to the anhydrous solid. Instead the material is typically prepared in a solution with ethanol. It is commercially available and as a solution in ethanol. It is easily prepared in the laboratory by treating sodium metal with absolute ethanol:[3]
- 2 C2H5OH + 2 Na → 2 C2H5ONa + H2
An alternative, cheaper route involves the reaction of sodium hydroxide with anhydrous ethanol. This reaction suffers from incomplete conversion to the alkoxide, but for less stringent applications, full conversion is unimportant. The salt product may be purified by precipitation in a solution of anhydrous acetone[4] An improvement to this process involves removing generated water with molecular sieves [5]
Reactions
The solid gradually turns dark on storage in dry air because of oxidation.[6] In moist air, it hydrolyzes rapidly to sodium hydroxide. The conversion is not obvious and typical samples of NaOEt are contaminated with NaOH.
Sodium ethoxide is commonly used in the Claisen condensation and malonic ester synthesis. Sodium ethoxide may either deprotonate the α-position of an ester molecule, forming an enolate, or the ester molecule may undergo a nucleophilic substitution called transesterification. If the starting material is an ethyl ester, trans-esterification is irrelevant since the product is identical to the starting material. In practice, the alcohol/alkoxide solvating mixture must match the alkoxy components of the reacting esters to minimize the number of different products.
Many alkoxides are prepared by salt metathesis from sodium ethoxide.
Safety
Sodium ethoxide is a strong base, and is therefore corrosive.
See also
References
- ^ disassociation constant of Ethanol, referenced in the CRC Handbook of Chemistry and Physics 87th edition.
- ^ K. Sinclair Whitaker, D. Todd Whitaker, "Sodium Ethoxide" Encyclopedia of Reagents for Organic Synthesis 2001.doi:10.1002/047084289X.rs070
- ^ C. S. Marvel and E. E. Dreger (1926). "Ethyl Acetopyruvate". Organic Syntheses. 6: 40; Collected Volumes, vol. 1, p. 328.
- ^ US patent 1978647, Olson, E. & Twining, R. H., "Method for Making Alkali Metal Alcoholates", issued 1934-10-30
- ^ US patent 3479381, Mitchell M., "Preparation of Metal Alkoxides", issued 1969-11-18
- ^ M. Eagleson "Concise encyclopedia chemistry" p.997.