The benzoin condensation is a reaction (often called a condensation reaction

Condensation reaction

A condensation reaction is a chemical reaction in which two molecules or moieties combine to form one single molecule, together with the loss of a small molecule. When this small molecule is water, it is known as a dehydration reaction; other possible small molecules lost are hydrogen chloride,...

, for historical reasons) between two aromatic aldehyde

Aldehyde

An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....

s, particularly benzaldehyde

Benzaldehyde

Benzaldehyde is an organic compound consisting of a benzene ring with a formyl substituent. It is the simplest aromatic aldehyde and one of the most industrially useful. This colorless liquid has a characteristic pleasant almond-like odor...

. The reaction is catalyzed

Catalysis

Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....

 by a nucleophile

Nucleophile

A nucleophile is a species that donates an electron-pair to an electrophile to form a chemical bond in a reaction. All molecules or ions with a free pair of electrons can act as nucleophiles. Because nucleophiles donate electrons, they are by definition Lewis bases.Nucleophilic describes the...

 such as the cyanide

Cyanide

A cyanide is a chemical compound that contains the cyano group, -C≡N, which consists of a carbon atom triple-bonded to a nitrogen atom. Cyanides most commonly refer to salts of the anion CN−. Most cyanides are highly toxic....

 anion or an N-heterocyclic carbene

Persistent carbene

A persistent carbene is a type of carbene demonstrating particular stability. The best-known examples are diaminocarbenes with the general formula 2C:, where the 'R's are various functional groups...

. The reaction product is an aromatic acyloin

Acyloin

Acyloins are a class of organic compounds in organic chemistry sharing a common functional group consisting of a hydroxyl group placed on the α-position of a carbonyl group.- Nomenclature :Common types of ketols include:...

 with benzoin

Benzoin

Benzoin is an organic compound with the formula PhCHCPh. It is a hydroxy ketone attached to two phenyl groups. It appears as off-white crystals, with a light camphor-like odor. Benzoin is synthesized from benzaldehyde in the benzoin condensation...

 as the parent compound. An early version of the reaction was developed in 1832 by Justus von Liebig

Justus von Liebig

Justus von Liebig was a German chemist who made major contributions to agricultural and biological chemistry, and worked on the organization of organic chemistry. As a professor, he devised the modern laboratory-oriented teaching method, and for such innovations, he is regarded as one of the...

 and Friederich Woehler during their research on bitter almond oil

Almond

The almond , is a species of tree native to the Middle East and South Asia. Almond is also the name of the edible and widely cultivated seed of this tree...

. The catalytic version of the reaction was developed by Nikolay Zinin

Nikolay Zinin

Nikolay Nikolaevich Zinin was a Russian organic chemist.-Life:He studied at the University of Kazan where he graduated in mathematics but he started teaching chemistry in 1835. To improve his skills he was asked to study in Europe for some time, which he did between 1838 and 1841...

 in the late 1830s, and the reaction mechanism

Reaction mechanism

In chemistry, a reaction mechanism is the step by step sequence of elementary reactions by which overall chemical change occurs.Although only the net chemical change is directly observable for most chemical reactions, experiments can often be designed that suggest the possible sequence of steps in...

 for this organic reaction

Organic reaction

Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, photochemical reactions and redox reactions. In organic synthesis,...

 was proposed in 1903 by A. J. Lapworth

Arthur Lapworth

Arthur Lapworth was a Scottish chemist.He was born in Galashiels, Scotland, the son of geologist Charles Lapworth and educated at St Andrew's and King Edward's School, Birmingham. He graduated in Chemistry from Mason College...

.
In the first step in this reaction, the cyanide anion (as sodium cyanide) reacts with the aldehyde in a nucleophilic addition

Nucleophilic addition

In organic chemistry, a nucleophilic addition reaction is an addition reaction where in a chemical compound a π bond is removed by the creation of two new covalent bonds by the addition of a nucleophile....

.