Sodium ethoxide, also referred to as sodium ethylate, is the ionic,

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon- hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...

with the formula , or NaOEt (Et =

ethane Ethane ( , ) is an organic chemical compound with chemical formula . At standard temperature and pressure, ethane is a colorless, odorless gas. Like many hydrocarbons, ethane is isolated on an industrial scale from natural gas and as a petro ...

). It is a white solid, although impure samples appear yellow or brown. It dissolves in polar solvents such as

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a h ...

. It is commonly used as a strong base.

Preparation

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

. It is easily prepared in the laboratory by treating

sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...

metal with absolute

: : The reaction of sodium hydroxide with anhydrous ethanol suffers from incomplete conversion to the alkoxide.

Structure

The crystal structure of sodium ethoxide has been determined by

X-ray crystallography X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angle ...

. It consists of layers of alternating Na⁺ and O⁻ centres with disordered

ethyl group In organic chemistry, an ethyl group (abbr. Et) is an alkyl substituent with the formula , derived from ethane (). ''Ethyl'' is used in the International Union of Pure and Applied Chemistry's nomenclature of organic chemistry for a saturat ...

s covering the top and bottom of each layer. The ethyl layers pack back-to-back resulting in a

lamellar structure In materials science, lamellar structures or microstructures are composed of fine, alternating layers of different materials in the form of lamellae. They are often observed in cases where a phase transition front moves quickly, leaving behin ...

. The reaction of sodium and ethanol sometimes forms other products such as the disolvate NaOEt·2EtOH. Its crystal structure has been determined, although the structure of other phases in the Na/EtOH system remain unknown.

Reactions

Sodium ethoxide is commonly used as a base in the

Claisen condensation The Claisen condensation is a carbon–carbon bond forming reaction that occurs between two esters or one ester and another carbonyl compound in the presence of a strong base, resulting in a β-keto ester or a β- diketone. It is named after Ra ...

and malonic ester synthesis. Sodium ethoxide may either deprotonate the α-position of an ester molecule, forming an

enolate In organic chemistry, enolates are organic anions derived from the deprotonation of carbonyl () compounds. Rarely isolated, they are widely used as reagents in the synthesis of organic compounds. Bonding and structure Enolate anions are electr ...

, or the ester molecule may undergo a

nucleophilic substitution In chemistry, a nucleophilic substitution is a class of chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass c ...

called

transesterification In organic chemistry, transesterification is the process of exchanging the organic group R″ of an ester with the organic group R' of an alcohol. These reactions are often catalyzed by the addition of an acid or base catalyst. The reaction ca ...

. 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

Sodium ethoxide is prone to reaction with both water and carbon dioxide in the air. 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. File:Sodium-ethoxide-reagent-bottle.jpg, New bottle of sodium ethoxide from Sigma-Aldrich File:Sodium-ethoxide-reagent-contents.jpg, Freshly opened container of sodium ethoxide showing discoloration caused by degradation when stored over oxygen and carbon dioxide. In moist air, NaOEt hydrolyses rapidly to sodium hydroxide (NaOH). The conversion is not obvious and typical samples of NaOEt 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. This instability can be prevented by storing sodium ethoxide under an inert () atmosphere.

Safety

Sodium ethoxide is a strong base, and is therefore corrosive.

References