The Benzoin condensation is a condensation reaction between two aromatic aldehydes, especially benzaldehyde that is catalyzed by a cyanide. The reaction product is an aromatic α-hydroxyketone with benzoin as the parent compound. The reaction mechanism for this organic reaction was already proposed in 1903 by A. J. Lapworth. A condensation reaction (also known as a dehydration reaction or dehydration synthesis when water is lost) is a chemical reaction in which two molecules or moieties react and become covalently bonded to one another by the concurrent loss of a small molecule, often water or methanol. ... In chemistry, an aromatic molecule is one in which electrons are free to cycle around circular arrangements of atoms, which are alternately singly and doubly bonded to one another. ... An aldehyde is either a functional group consisting of a terminal carbonyl group or a compound containing a terminal carbonyl group. ... The chemical compound benzaldehyde (C6H5CHO) consists of a benzene ring with an aldehyde group attached to one carbon. ... Generic graph showing the effect of a catalyst in an hypotetical exothermic chemical reaction. ... A cyanide is any chemical compound that contains the cyano group C≡N, with the carbon atom triple-bonded to the nitrogen atom. ... Benzoin is also used to describe benzoin resin, which does not contain the benzoin described on this page. ... In chemistry, a reaction mechanism is the step by step sequence of elementary reactions by which overall chemical change occurs. ... Organic reactions are chemical reactions between organic compounds. ...

In the first step in this reaction the cyanide ion (as sodium cyanide) reacts with the aldehyde in a nucleophilic addition. Umpolung reverses the polarity of the carbonyl group and the rearranged intermediate adds to the second carbonyl group in a second nucleophilic addition. Proton transfer and elimination of the cyanide ion affords the benzoin. This is a reversible reaction. The cyanide ion is a very specific catalyst and serves three different purposes in the course of the reaction. It acts as a nucleophile, it facilitates proton abstraction in the umpolung by its inductive effect and it is also the leaving group in the final step. The benzoin condensation is in effect a dimerization and not a condensation because a small molecule like water is not released in this reaction. For this reason the reaction is also called a benzoin addition. Both aldehydes have a different purpose. One aldehyde donates a proton and one aldehyde accepts a proton. 4-Dimethylaminobenzaldehyde is an efficient proton donor while benzaldehyde is both a proton and a donor. In this way it is possible to synthesise asymmetric benzoins. Image File history File links Benzoin. ... In organic chemistry, a nucleophilic addition reaction is an addition reaction where in a chemical compound a pi bond is removed by the creation of two new covalent bonds by the addition of a nucleophile. ... Umpolung or polarity inversion in organic chemistry is the chemical modification of a functional group with the aim the reversal of polarity of that group. ... layers]] that separate organs or subcompartments in organisms. ... Hydronium is the common name for the cation H3O+. Nomenclature According to IUPAC ion nomenclature, it should be referred to as oxonium. ... A reversible reaction is a chemical reaction that may be reversed. ... A catalyst (Greek: καταλύτης, catalytēs) is a substance that accelerates the rate (speed) of a chemical reaction (see also catalysis). ... In chemistry, a nucleophile (literally nucleus lover) is a reagent which is attracted to centres of positive charge. ... The inductive effect is associated with the dipole moment of the compound R-X. If X is at the negative end of a dipole moment, it will draw electrons from the ring and produce -I effect. ... A leaving group is an atom or molecule that detaches from an organic molecule, which, after detachment, is called the residual or main part. ... Dimerization is the formation of a polymer from two similar chemical structures. ...

The reaction can be extended to aliphatic aldehydes with base catalysis in the presence of thiazolium salts. The reaction mechanism is essencially the same. The corresponding product is called an acyloine. These compounds are important in the synthesis of heterocyclic compounds. The addition is also possible with α-β-unsaturated ketones for instance methylvinylketon in the Stetter reaction. In chemistry, non-aromatic and non-cyclic (acyclic) organic compounds are called aliphatic. ... The common (Arrhenius) definition of a base is a chemical compound that absorbs hydronium ions when dissolved in water (a proton acceptor). ... Wikipedia does not yet have an article with this exact name. ...

In biochemistry, the coenzyme Thiamine is responsible for biosynthesis of acyloine-like compounds. This coenzyme also contains a thiazolium moiety. Biochemistry is the study of the chemistry of life, a bridge between biology and chemistry that studies how complex chemical reactions give rise to life. ... A coenzyme (a. ... Thiamine mononitrate Thiamine or thiamin, also known as vitamin B1, is a colorless compound with chemical formula C12H17N4OS. It is soluble in water and insoluble in alcohol. ...

References

• Main text & image German Wiki original
• CXXII.—Reactions involving the addition of hydrogen cyanide to carbon compounds. Part II. Cyanohydrins regarded as complex acids Arthur Lapworth, Journal of the Chemical Society, Transactions, 1904, 85, 1206 - 1214 Abstract
• Benzoin Roger Adams and C. S. Marvel Organic Syntheses, Coll. Vol. 1, p.94; Vol. 1, p.33 Article