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| Names | |
|---|---|
| IUPAC name Sodium ethoxide | |
| Other names Sodium ethanolate, sodium ethylate (obsolete) | |
| Identifiers | |
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3D model (JSmol) | |
| 3593646 | |
| ChEBI | |
| ChemSpider |
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| ECHA InfoCard | 100.004.989 |
| EC Number |
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| UNII | |
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| Properties | |
| CH3CH2ONa | |
| Molar mass | 68.051 g·mol−1 |
| Appearance | Whitehygroscopic powder |
| Density | 0.868 g/cm3 (of a 21 wt% solution in ethanol) |
| Melting point | 260 °C (500 °F; 533 K) |
| Reacts | |
| Solubility | ethanol andmethanol |
| Acidity (pKa) | 15.5[1] |
| Hazards | |
| GHS labelling: | |
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| Danger | |
| H228,H251,H302,H314 | |
| P210,P235+P410,P240,P241,P260,P264,P270,P280,P301+P312,P301+P330+P331,P303+P361+P353,P304+P340,P305+P351+P338,P310,P321,P330,P363,P370+P378,P405,P407,P413,P420,P501 | |
| NFPA 704 (fire diamond) | |
| Safety data sheet (SDS) | Oxford MSDS |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Sodium ethoxide, also referred to assodium ethanolate, is theionic,organic compound with the formulaCH3CH2ONa,C2H5ONa, or NaOEt (Et =ethyl). It is a white solid, although impure samples appear yellow or brown. It dissolves in polar solvents such asethanol. It is commonly used as a strongbase.[2]
Few procedures have been reported to prepare 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 treatingsodium metal with absoluteethanol:[3]
The reaction ofsodium hydroxide with anhydrous ethanol suffers from incomplete conversion to the ethoxide, but can still produce dry NaOEt by precipitation using acetone,[4] or by drying using additional NaOH.[5]
Sodium ethoxide is commonly used as a base in theClaisen condensation[6] andmalonic ester synthesis.[7] Sodium ethoxide may either deprotonate the α-position of anester molecule, forming anenolate, or the ester molecule may undergo anucleophilic substitution calledtransesterification. 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.
Manyalkoxides are prepared bysalt metathesis from sodium ethoxide.
Sodium ethoxide is prone to reaction with both water andcarbon dioxide in theair.[8] This leads to degradation of stored samples over time, even in solid form. The physical appearance of degraded samples may not be obvious, but samples of sodium ethoxide gradually turn dark on storage. It has been reported that even newly-obtained commercial batches of sodium ethoxide show variable levels of degradation, and responsible as a major source of irreproducibility when used inSuzuki reactions.[8]
In moist air,CH3CH2ONahydrolyses rapidly tosodium hydroxide (NaOH). The conversion is not obvious and typical samples ofCH3CH2ONa are contaminated with NaOH.
Inmoisture-free air, solid sodium ethoxide can form sodium ethyl carbonate from fixation of carbon dioxide from the air. Further reactions lead to degradation into a variety of other sodiumsalts anddiethyl ether.[8]
This instability can be prevented by storing sodium ethoxide under aninert atmosphere (e.g.,N2).
The crystal structure of sodium ethoxide has been determined byX-ray crystallography. It consists of layers of alternatingNa+ andO− centres with disorderedethyl groups covering the top and bottom of each layer. The ethyl layers pack back-to-back resulting in alamellar structure. The reaction of sodium and ethanol sometimes forms other products such as the disolvateCH3CH2ONa·2CH3CH2OH. Its crystal structure has been determined, although the structure of other phases in theCH3CH2ONa/CH3CH2OH system remain unknown.[9]
 |  |  |
| ball-and-stick model of layer stacking in the crystal structure ofCH3CH2ONa | coordination geometry at Na | coordination geometry at O |
Sodium ethoxide is a strongbase, and is therefore corrosive.
