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Benzoin Condensation and Perkin Condensation

Chemistry tells us how matter forms, how new substances are formed, and what the results of those reactions are.

Benzoin condensation

Chemistry tells us how matter forms, how new substances are formed, and what the results of those reactions are. These reactions give us a better understanding of the properties of matter. Condensation of aldehydes into benzoin explains the formation of the chemical compound. This reaction was discovered by Justus von Liebig and Friederich Woehler in 1832.

An aromatic compound can be formed by converting two kinds of aromatic aldehydes, more specifically benzaldehyde, in the presence of an initiating catalyst (for example, a nucleophile or heterocyclic). Carbon-to-carbon bonds, polymers, monomers, polypeptides, and various polymerization reactions are created by condensation reactions. It is the coupling reaction between aldehydes that produces parent benzoin in the benzoin condensation reaction. This homocoupling process is carried out by the benzaldehyde.

Mechanism




Condensation reactions take the following general form:



The condensation reaction of benzoin involves these steps:
  • Cyanide ions react first with benzaldehyde to produce cyanohydrin, which is the first product formed during the process. A nucleophilic addition reaction is carried out in this step by the cyanide ion or sodium cyanide, and it is reversible. In this reaction, the cyanide ion acts as a nucleophile and facilitates the abstraction of protons in order to form cyanohydrin. This reaction is catalyzed by cyanide ions.
  • In the second step, cyanohydrin is reacting with benzaldehyde to form a condensation product.
  • The third phase involves the rearrangement of the molecules and the removal of the cyanide ions, which results in the formation of benzoin. After the rearrangement process takes place, the carbonyl group reverses polarity, adding to the second group of carbonyl atoms in the nucleophilic addition.
An aldehyde reacts with an aldehyde and a strong base deprotonates the carbonyl C-atom, resulting in the elimination of the catalyst and the regeneration of the carbonyl compound at the end of the condensation reaction. The two different aldehydes in the Benzoin Condensation reaction serve two purposes. The aldehydes in the reaction donate protons to one another and accept them from the other.

The Benzoin Condensation Reaction and its Application

  • There are various organic reactions and synthesises that use benzoin condensation reactions.
  • Benzoin is used in the process of hardening different polymers using microemulsions.
  • The reaction is useful when synthesizing heterocyclic compounds, as well as for aldehydes in their aliphatic forms.
  • As well as in poly-chemistry, these reactions can be used to produce polymers and to form new monomers.

Perkin condensation

Perkin Reaction is the result of an organic chemical reaction discovered by an English chemist named William Henry Perkin in 1879. A α, β -unsaturated aromatic acid result from this reaction. Cinnamic acid derivatives are made from the reaction between aromatic aldehydes, aliphatic acid anhydride, and the alkaline salt of the acid in the Perkin reaction mechanism. William Henry Perkin is credited with discovering the Perkin reaction, which is an organic chemical reaction.

The Perkin reaction results in a alpha, beta-unsaturated aromatic acid when an aldehyde and an acid anhydride are combined.This reaction also produces the acid's alkali salt. Alkali salts are catalysts that act as bases. Perkin reactions can also be conducted with other bases in place of the alkali salts of acids.

The reaction of Perkin is illustrated below.



Resveratrol is a phyto-estrogenic stilbene that is synthesized in the laboratory via the Perkin reaction. Condensation reactions are the basis of the Perkin reaction.

Mechanism

A carbanion is formed when the anhydride reacts with the base. In this case, the carbanion is attacking the carbonyl carbon of the aldehyde. An intermediate is obtained with this attack. Adding the given base to an intermediate results in protonation of the methyl group, followed by the removal of the hydroxyl group, resulting in an unsaturated anhydride. The final result of hydrolyzing this product is alpha, beta-unsaturated acid. As an illustration of Perkin's reaction, we have the following diagram:.



Consequently, the necessary alpha, beta-unsaturated acids are formed.

There are numerous variations to the mechanism of Perkin reaction, and the above-given mechanism is not universally accepted. In addition to decarboxylation without transfer of an acetyl group, there are other mechanisms linked to decarboxylation.
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Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of Pharmaceutical Guidelines, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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