The Favorskii reaction is an
organic chemistry reaction between an
alkyne
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Acetylene
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Propyne
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1-Butyne
In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and n ...
and a
carbonyl group, under
basic
BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages designed for ease of use. The original version was created by John G. Kemeny and Thomas E. Kurtz at Dartmouth College ...
conditions. The reaction was discovered in the early 1900s by the Russian chemist
Alexei Yevgrafovich Favorskii.
When the carbonyl is an
aldehyde (R"=H), a
rearrangement can occur to generate
enone, although the secondary propargylic alcohol can be isolated in some cases. When this rearrangement is catalyzed by an
acid
In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequ ...
, it is called
Meyer–Schuster rearrangement.
Reaction mechanism and scope
A
metal acetylide is formed ''
in situ'' when an
alkyne
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Acetylene
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Propyne
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1-Butyne
In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and n ...
is treated with a strong
bases such as a
hydroxide or an
alkoxide
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, whe ...
:
# HC≡CH + KOH HC≡CK + H
2O
# RR'C=O + HC≡CK RR'C(OK)C≡CH
The metal acetylide then reacts with an aldehyde or ketone to form a
propargyl alcohol
Propargyl alcohol, or 2-propyn-1-ol, is an organic compound with the chemical formula, formula C3H4O. It is the simplest stable Alcohol (chemistry), alcohol containing an alkyne functional group. Propargyl alcohol is a colorless viscous liquid t ...
. When an
α-hydrogen is present (as is the case when the carbonyl is an
aldehyde), it will
tautomerize to the corresponding
enone.
[
The applicable ]substrate
Substrate may refer to:
Physical layers
*Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached
** Substrate (locomotion), the surface over which an organism lo ...
s that undergo a Favorskii reaction are limited when compared to the conventional reaction because using an excess of hydroxide base introduces aldol condensation as a more significant competing side reaction.1,2-dimethoxyethane
Dimethoxyethane, also known as glyme, monoglyme, dimethyl glycol, ethylene glycol dimethyl ether, dimethyl cellosolve, and DME, is a colorless, aprotic, and liquid ether that is used as a solvent, especially in batteries. Dimethoxyethane is misc ...
with a trace amount of ethanol.reagent
In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a ...
s such as elemental lithium, sodium, or potassium. Additionally, the stringent reaction conditions used by most alternatives, such as excluding moisture and atmospheric oxygen, are less important, making the reaction easier to perform.
Protecting group
This reaction is used to protect alkyne
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Acetylene
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Propyne
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1-Butyne
In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and n ...
s: the alkyne is either converted with acetone to a 2-hydroxyprop-2-yl-alkyne or a protected alkyne can be directly synthesized using the commercially available 2-methyl-3-butyn-2-ol as an alkyne source. The protective group can be removed by heating the compound in a solution of potassium hydroxide in propan-2-ol (a retro-Favorskii reaction).
See also
* Alkynation
References
{{DEFAULTSORT:Favorskii Reaction
Rearrangement reactions
Name reactions
Carbon-carbon bond forming reactions