The Bouveault–Blanc reduction is a
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 changes that only involve the positions of electrons in the forming and break ...
in which an
ester
In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ...
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
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 hyd ...
and
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.
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
Oleyl alcohol , or ''cis''-9-octadecen-1-ol, is an unsaturated fatty alcohol with the molecular formula or the condensed structural formula . It is a colorless oil, mainly used in cosmetics.
It can be produced by the hydrogenation of oleic ac ...
. 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 exper ...
''.
:
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 Li Al H4. It is a white solid, discovered by Finholt, Bond and Schlesinger in 1947. This compound is used as a reducing agent in organic ...
.
Reaction mechanism
Sodium metal is a one-electron reducing agent. Four equivalents of sodium are required to fully reduce each ester.
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 ...
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 organic substituent. Alkoxides are strong bases and, wh ...
, 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.
[ The mechanism of the reaction follows:]lithium aluminium hydride
Lithium aluminium hydride, commonly abbreviated to LAH, is an inorganic compound with the chemical formula Li Al H4. It is a white solid, discovered by Finholt, Bond and Schlesinger in 1947. This compound is used as a reducing agent in organic ...
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 porous form of silicon dioxide (silica), consisting of an irregular tridimensional framework of alternating silicon and oxygen atoms with nanometer-scale voids and pores. The voids may contain water or some other ...
, 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 is an organic reaction that is used to convert arenes to cyclohexadienes. The reaction is named after the Australian chemist Arthur Birch and involves the organic reduction of aromatic rings in an amine solvent (traditional ...
– For the reduction of alkenes using sodium
*Bouveault aldehyde synthesis
The Bouveault aldehyde synthesis (also known as the Bouveault reaction) is a one-pot substitution reaction that replaces an alkyl or aryl halide with a formyl group using a ''N'',''N''-disubstituted formamide.
For primary alkyl halides this produc ...
– 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