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The Bouveault–Blanc reduction is a
chemical reaction A chemical reaction is a process that leads to the chemistry, chemical transformation of one set of chemical substances to another. When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an Gibbs free energy, ...
in which an
ester In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distin ...
is reduced to
primary alcohol A primary alcohol is an alcohol in which the hydroxy group is bonded to a primary carbon atom. It can also be defined as a molecule containing a “–CH2OH” group. In contrast, a secondary alcohol has a formula “–CHROH” and a tertiary ...
s using absolute ethanol and
sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...
metal. It was first reported by Louis Bouveault and Gustave Louis Blanc in 1903. Bouveault and Blanc demonstrated the reduction of ethyl oleate and ''n''- butyl oleate to oleyl alcohol. Modified versions of which were subsequently refined and published in ''
Organic Syntheses ''Organic Syntheses'' is a peer-reviewed scientific journal that was established in 1921. It publishes detailed and checked procedures for the synthesis of organic compounds. A unique feature of the review process is that all of the data and expe ...
''. : This reaction is used commercially although for laboratory scale reactions it was made obsolete by the introduction of
lithium aluminium hydride Lithium aluminium hydride, commonly abbreviated to LAH, is an inorganic compound with the chemical formula or . It is a white solid, discovered by Finholt, Bond and Schlesinger in 1947. This compound is used as a reducing agent in organic synthe ...
.


Reaction mechanism

Sodium metal is a one-electron reducing agent. Four equivalents of sodium are required to fully reduce each ester, although two more equivalents are typically consumed in deprotonating the product alcohols to alkoxides.
Ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...
serves as a proton source. The reaction produces sodium
alkoxides In chemistry, an alkoxide is the conjugate base of an alcohol and therefore consists of an organic group bonded to a negatively charged oxygen atom. They are written as , where R is the organyl substituent. Alkoxides are strong bases and, when ...
, according to the following stoichiometry: :   +   6 Na   +   4    →     +     +   4  In practice, considerable sodium is consumed by the formation of hydrogen. For this reason, an excess of sodium is often required. Because the hydrolysis of sodium is rapid, not to mention dangerous, the Bouveault–Blanc reaction requires anhydrous ethanol and can give low yields with insufficiently dry ethanol. The mechanism of the reaction follows: : Consistent with this mechanism, sodium-ethanol mixtures will also reduce ketones to alcohols. This approach to reducing esters was widely used prior to the availability of hydride reducing agents such as
lithium aluminium hydride Lithium aluminium hydride, commonly abbreviated to LAH, is an inorganic compound with the chemical formula or . It is a white solid, discovered by Finholt, Bond and Schlesinger in 1947. This compound is used as a reducing agent in organic synthe ...
and related reagents. It requires vigorous reaction conditions and has a significant risk of fires, explaining its relative unpopularity. One modification involves encapsulating the alkali metal into a
silica gel Silica gel is an amorphous and porosity, porous form of silicon dioxide (silica), consisting of an irregular three-dimensional framework of alternating silicon and oxygen atoms with nanometer-scale voids and pores. The voids may contain wate ...
, which has a safety and yield profile similar to that of hydride reagents. Another modification uses a sodium dispersion.


See also

* Acyloin condensation – The reductive coupling of esters, using sodium, to yield an α-hydroxyketone * Akabori amino-acid reaction – The reduction of amino acid esters, by sodium, to yield aldehydes *
Birch reduction The Birch reduction or Metal-Ammonia reduction is an organic reaction that is used to convert arenes to Cyclohexa-1,4-diene, 1,4-cyclohexadienes. The reaction is named after the Australian chemist Arthur Birch (organic chemist), Arthur Birch and i ...
– For the reduction of alkenes using sodium * Bouveault aldehyde synthesis – Another organometallic reaction by Bouveault where a Grignard reagent is converted to an aldehyde


References


External links


Animation of the Bouveault–Blanc reduction
{{DEFAULTSORT:Bouveault-Blanc reduction Free radical reactions Organic redox reactions Name reactions