Sodium ethoxide, also referred to as sodium ethanolate, is the ionic, organic compound with the formula CH3CH2ONa, C2H5ONa, or NaOEt (Et = ethyl). It is a white solid, although impure samples appear yellow or brown. It dissolves in polar solvents such as ethanol. It is commonly used as a strong base.[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 treating sodium metal with absolute ethanol:[3]
The reaction of sodium hydroxide with anhydrous ethanol suffers from incomplete conversion to the ethoxide.
Structureedit
The crystal structure of sodium ethoxide has been determined by X-ray crystallography. It consists of layers of alternating Na+ and O− centres with disordered ethyl groups covering the top and bottom of each layer. The ethyl layers pack back-to-back resulting in a lamellar structure. The reaction of sodium and ethanol sometimes forms other products such as the disolvate CH3CH2ONa·2CH3CH2OH. Its crystal structure has been determined, although the structure of other phases in the CH3CH2ONa/CH3CH2OH system remain unknown.[4]
Sodium ethoxide is commonly used as a base in the Claisen condensation[5] and malonic ester synthesis.[6] 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.
Sodium ethoxide is prone to reaction with both water and carbon dioxide in the air.[7] 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 in Suzuki reactions.[7]
New bottle of sodium ethoxide from Sigma-Aldrich
Freshly opened container of sodium ethoxide showing discoloration caused by degradation when stored over oxygen and carbon dioxide.
In moist air, CH3CH2ONahydrolyses rapidly to sodium hydroxide (NaOH). The conversion is not obvious and typical samples of CH3CH2ONa are contaminated with NaOH.
In moisture-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 sodium salts and diethyl ether.[7]
This instability can be prevented by storing sodium ethoxide under an inert atmosphere (e.g., N2).
Safetyedit
Sodium ethoxide is a strong base, and is therefore corrosive.
^disassociation constant of ethanol, referenced in the CRC Handbook of Chemistry and Physics 87th edition.
^K. Sinclair Whitaker; D. Todd Whitaker (2001). "Sodium Ethoxide". In Charette, André B. (ed.). Encyclopedia of Reagents for Organic Synthesis. John Wiley & Sons. doi:10.1002/047084289X.rs070. ISBN978-0-470-84289-8.
^C. S. Marvel, E. E. Dreger (1926). "Ethyl Acetopyruvate". Organic Syntheses. 6: 40. doi:10.15227/orgsyn.006.0040.
^M. Beske; L. Tapmeyer; M. U. Schmidt (2020). "Crystal structure of sodium ethoxide (C2H5ONa), unravelled after 180 years". Chem. Commun.56 (24): 3520–3523. doi:10.1039/C9CC08907A. PMID 32101200. S2CID 211523921.
^Clayden, Jonathan; Greeves, Nick; Warren, Stuart (2012). Organic chemistry (2nd ed.). New York: Oxford University Press. p. 645. ISBN978-0-19-927029-3.
^Wang, Zerong (15 September 2010). Comprehensive organic name reactions and reagents. John Wiley. pp. 1811–1815. ISBN978-0-471-70450-8.
^ abcWethman, Robert; Derosa, Joseph; Tran, Van; Kang, Taeho; Apolinar, Omar; Abraham, Anuji; Kleinmans, Roman; Wisniewski, Steven; Coombs, John; Engle, Keary (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 (ACS), doi:10.26434/chemrxiv.12818234.v1, S2CID 242420220
May 02, 2024
sodium, ethoxide, also, referred, sodium, ethanolate, ionic, organic, compound, with, formula, ch3ch2ona, c2h5ona, naoet, ethyl, white, solid, although, impure, samples, appear, yellow, brown, dissolves, polar, solvents, such, ethanol, commonly, used, strong, . Sodium ethoxide also referred to as sodium ethanolate is the ionic organic compound with the formula CH3CH2ONa C2H5ONa or NaOEt Et ethyl It is a white solid although impure samples appear yellow or brown It dissolves in polar solvents such as ethanol It is commonly used as a strong base 2 Sodium ethoxide Names Other names Sodium ethanolate sodium ethylate obsolete Identifiers CAS Number 141 52 6 Y 3D model JSmol Interactive image Beilstein Reference 3593646 ChEBI CHEBI 52096 ChemSpider 8516 Y ECHA InfoCard 100 004 989 EC Number 205 487 5 PubChem CID 2723922 UNII 1I9504387J CompTox Dashboard EPA DTXSID3027089 InChI InChI 1S C2H5O Na c1 2 3 h2H2 1H3 q 1 1 YKey QDRKDTQENPPHOJ UHFFFAOYSA N YInChI 1 C2H5O Na c1 2 3 h2H2 1H3 q 1 1Key QDRKDTQENPPHOJ UHFFFAOYAQ SMILES Na O CC Properties Chemical formula CH3CH2ONa Molar mass 68 051 g mol 1 Appearance White hygroscopic powder Density 0 868 g cm3 of a 21 wt solution in ethanol Melting point 260 C 500 F 533 K Solubility in water Reacts Solubility ethanol and methanol Acidity pKa 15 5 1 Hazards GHS labelling Pictograms Signal word Danger Hazard statements H228 H251 H302 H314 Precautionary statements 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 221W 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 N verify what is Y N Infobox references Contents 1 Preparation 2 Structure 3 Reactions 4 Stability 5 Safety 6 See also 7 ReferencesPreparation editFew 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 treating sodium metal with absolute ethanol 3 2 CH3CH2OH 2 Na 2 CH3CH2ONa H2 The reaction of sodium hydroxide with anhydrous ethanol suffers from incomplete conversion to the ethoxide Structure editThe crystal structure of sodium ethoxide has been determined by X ray crystallography It consists of layers of alternating Na and O centres with disordered ethyl groups covering the top and bottom of each layer The ethyl layers pack back to back resulting in a lamellar structure The reaction of sodium and ethanol sometimes forms other products such as the disolvate CH3CH2ONa 2CH3CH2OH Its crystal structure has been determined although the structure of other phases in the CH3CH2ONa CH3CH2OH system remain unknown 4 nbsp nbsp nbsp ball and stick model of layer stacking in the crystal structure of CH3CH2ONa coordination geometry at Na coordination geometry at OReactions editSodium ethoxide is commonly used as a base in the Claisen condensation 5 and malonic ester synthesis 6 Sodium ethoxide may either deprotonate the a 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 Stability editSodium ethoxide is prone to reaction with both water and carbon dioxide in the air 7 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 in Suzuki reactions 7 nbsp New bottle of sodium ethoxide from Sigma Aldrich nbsp Freshly opened container of sodium ethoxide showing discoloration caused by degradation when stored over oxygen and carbon dioxide In moist air CH3CH2ONa hydrolyses rapidly to sodium hydroxide NaOH The conversion is not obvious and typical samples of CH3CH2ONa are contaminated with NaOH In moisture 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 sodium salts and diethyl ether 7 This instability can be prevented by storing sodium ethoxide under an inert atmosphere e g N2 Safety editSodium ethoxide is a strong base and is therefore corrosive See also editAlkoxide Phenolate Sodium methoxide Sodium phenoxide Potassium methoxide Potassium ethoxideReferences edit disassociation constant of ethanol referenced in the CRC Handbook of Chemistry and Physics 87th edition K Sinclair Whitaker D Todd Whitaker 2001 Sodium Ethoxide In Charette Andre B ed Encyclopedia of Reagents for Organic Synthesis John Wiley amp Sons doi 10 1002 047084289X rs070 ISBN 978 0 470 84289 8 C S Marvel E E Dreger 1926 Ethyl Acetopyruvate Organic Syntheses 6 40 doi 10 15227 orgsyn 006 0040 M Beske L Tapmeyer M U Schmidt 2020 Crystal structure of sodium ethoxide C2H5ONa unravelled after 180 years Chem Commun 56 24 3520 3523 doi 10 1039 C9CC08907A PMID 32101200 S2CID 211523921 Clayden Jonathan Greeves Nick Warren Stuart 2012 Organic chemistry 2nd ed New York Oxford University Press p 645 ISBN 978 0 19 927029 3 Wang Zerong 15 September 2010 Comprehensive organic name reactions and reagents John Wiley pp 1811 1815 ISBN 978 0 471 70450 8 a b c Wethman Robert Derosa Joseph Tran Van Kang Taeho Apolinar Omar Abraham Anuji Kleinmans Roman Wisniewski Steven Coombs John Engle Keary 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 ACS doi 10 26434 chemrxiv 12818234 v1 S2CID 242420220 Retrieved from https en wikipedia org w index php title Sodium ethoxide amp oldid 1183994569, wikipedia, wiki, book, books, library,
