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Perkin reaction is an organic chemical reaction that specifies the reaction between aromatic aldehydes, the aliphatic acid anhydride, and the alkali salt of the acid. The reaction is used in the preparation of cinnamic acid.
- Perkin Reaction Mechanism yields an α, β -unsaturated aromatic acid.
- The reaction was introduced by William Henry Perkin, an English chemist.
- It is also known as the Perkin Condensation Reaction.
- Perkin reaction comes under organic chemistry, which deals with carbon compounds.
- Cinnamic acid is a type of naturally occurring carboxylic acid through heating, aldehyde, and dehydration.
- The reaction is thermodynamically feasible and has been experimentally supported.
- In these reactions, alkali will act as a base catalyst.
- The reaction is carried out at 180 degree Celsius.
Key Terms: Perkin Reaction, Organic Chemistry, Perkin Condensation Reaction Mechanism, Aldol Condensation, Alpha-Carbon, Carbonyl Group, Aldehydes, Aliphatic Acid Anhydride, Aromatic Acid, Carboxylic Acid
What is Perkin Reaction?
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Perkin reaction is a type of reaction that yields a beta-unsaturated aromatic acid-containing carboxylic acid group by the aldol condensation of an aromatic aldehyde group.
- The reaction is carried out in the presence of an alkali salt of the acid.
- It acts as a base catalyst to increase the rate of reaction.
- Perkin reaction belongs to carbonyl compounds.
When the enolate of an aldehyde or a ketone reacts with the alpha-carbon, which is the carbon next to the carbonyl carbon, with the carbonyl of another molecule under basic or acidic conditions to obtain beta-hydroxy aldehyde or ketone.
- Beta means the second carbon atom next to the carbonyl group.
- This reaction is called “aldol condensation reaction”.
When an acid anhydride and aromatic aldehyde react with each other in the presence of a weak base, they condense ( remove water) to give the desired product.
Example of Perkin ReactionExample: The illustration of the perkin reaction is as follows-.  As mentioned above the mechanism involves the condensation of an aldehyde and carboxylic acid anhydride with a weak base acting as a catalyst.
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Perkin Reaction Procedure
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The reaction is carried out by heating the aldehyde with an excess of acid anhydride at 180°C. Mostly dehydration takes place under the conditions of the reaction.
- Excess aldehyde is removed by distillation in steam.
- It results in obtaining unsaturated acid by hydrolysis of the anhydride with dilute HCl.
Perkin Reaction Mechanism
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The following steps are followed in the mechanism of perkin condensation reaction -
- The very primary step is the removal of H+ ions using a weak base by carboxylate ion.
- It results in the formation of resonance stabilized carbanion.
- The next step involves the nucleophilic addition of carbanion to the carbonyl carbon of aldehyde.
- This results in the formation of a tetrahedral intermediate.
- The tetrahedral intermediate is added by the acetic acid formed in the process.
- This step involves the elimination of water molecules from the hydroxy derivative.
- Hydrolysis (addition of water) of the unsaturated compound to the unsaturated acid occurs.
Application of Perkin Reaction Mechanism
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The application of perkin reaction mechanism are as follows:
- Perkin reaction is used to make cinnamic acids.
- Cinnamic acids are carboxylic acids that occur naturally.
- The reaction is used to make α and β-unsaturated aromatic acids, which are used in the pharmaceutical sector.
- In laboratories, the reaction is generally used in the synthesis of phytoestrogenic stilbene Resveratrol.
- Perkin reaction helps in anticoagulation (clot formation inhibition) in areas of slowly running blood.
- It includes veins and the pooled blood behind artificial and natural valves.
- The reaction does not affect the thickness and viscosity of blood.
- It decreases the proteins in the body which allow blood to clot.
Things to Remember
- Perkins reaction is an organic type of reaction which is used to make cinnamic compounds.
- The organic compounds consist of carbon and its derivatives.
- It attacks the base on anhydride, which results in the formation of carbanions.
- It produces unsaturated anhydride with the elimination of the hydroxyl group.
- It includes a reaction between aromatic aldehydes, aliphatic acid anhydride, and alkali salt.
- One notable application for the Perkin reaction is in the laboratory synthesis of phytoestrogenic stilbene resveratrol.
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Sample Questions
Ques. What are the suitable bases for Perkin’s reaction? Which catalysts are used in Perkin’s condensation mechanism? (2 marks)
Ans. Suitable bases for the Perkin reaction are potassium carbonate and EDTA. Typically, the sodium salt of the acid is used as a base catalyst in the Perkin reaction. Sodium and Potassium salts are used as catalysts. The alkali salts act as a weak base that is suitable for reaction as a strong base causes undesirable changes.
Ques. How is cinnamic acid synthesized from benzaldehyde? Which Intermediate is Involved and what is the final product of the Perkin reaction. (2 marks)
Ans. Cinnamic acid is prepared by oxidation of benzal acetone which was synthesized by condensing benzaldehyde and acetone. To produce benzyl acetone, benzaldehyde was reacted with acetone in a 1% NaOH The intermediate involved in the reaction is a tetrahedral entity that is formed by attacking a carbanion on the carbonyl compound.
Ques. Write a short note on Perkins's reaction? What is the active methylene group name in the Perkin reaction? (2 marks)
Ans. Reaction of formaldehyde and another aldehyde which do not contain alpha hydrogen, with concentrated alkali solution is called Cannizzaro reaction. One aldehyde molecule gives sodium salt to the acid and the other gives alcohol.
C2H5CH = O+CH−CO−O−COCH3Δ → CH3−COONaC5H5CH = CH−COOH+CH3 COCH3 cinnamic acid.
Azlactone (have active methylene group) undergoes Perkin reaction with the aldehyde.
Ques. What will be the product of the following reaction given below? (2 marks)
Ans. These products are obtained due to the Cannizzaro reaction 
-and 
. is obtained due to self-aldol condensation of β−phenylacetaldehyde.
Ques. Which of the following is Perkins's reaction? (3 marks)
(a) 
(b) 
(c) 
(d) 
Ans. Option a)and b) are perkin reactions.
Ques. Explain perkin reaction with explained example? (2 marks)
Ans. In 4-nitrobenzaldehyde, the electron-withdrawing nitro group is present. It increases the positive charge on carbonyl carbon. Hence 4-nitro benzaldehyde is most reactive towards nucleophiles in the Perkins condensation reaction. However, when electron releasing groups are present in aromatic aldehydes, the positive charge on the carbonyl carbon decreases.
Hence such compounds are less reactive toward nucleophiles in the Perkins condensation reaction.
Ques. which will be reactive for Perkins condensation? (3 marks)
(a) 
(b) 
(c) 
(d) None of these
Ans. Correct option is C)
- This reaction occurs between an aromatic aldehyde and an aliphatic anhydride having at least two α−H atoms.
- Electron attracting groups attached to the ring increase the efficiency of Perkin condensation while electron releasing groups (electron-donating group) decrease the efficiency of Perkin's reaction.
Hence, option C will be the most reactive towards perkin's condensation.
Ques. Which of the following products will form? 
(2 marks)
Ans. 
Ques. Explain Perkin Reaction Mechanisms? (4 marks)
Ans. The process of perkin reaction is as follows:
- The elimination of H+ ions using a weak base by carboxylate ion is the first and most important step.
- The development of a resonance-stabilized carbanion is the outcome.
- The nucleophilic addition of carbanion to the aldehyde's carbonyl carbon is the following step.
- A tetrahedral intermediate is created as a result.
- The procedure produces acetic acid, which adds the tetrahedral intermediate.
- In this stage, the hydroxy derivative's water molecules are removed.
- The unsaturated molecule hydrolyzes, or absorbs more water, to become an unsaturated acid.
Ques. Mention the application of Perkin Reaction Mechanism? (3 marks)
Ans. The application of Perkinn Reaction Mechanisms are as follows:
- The pharmaceutical industry uses the process to produce α and β-unsaturated aromatic acids.
- The reaction is typically employed in lab settings to create the phytoestrogenic stilbene Resveratrol.
- In regions where blood flows slowly, the Perkin reaction aids in anticoagulation, or the suppression of clot formation.
- Veins and the blood accumulated behind both natural and artificial valves are included.
- The response has no effect on blood's viscosity or thickness.
- It lessens the body's production of proteins that promote blood clotting.
Ques. Explain Perkin Reaction catalyst? (2 marks)
Ans. An alkali salt of an acid anhydride is a catalyst that is frequently employed in the Perkin reaction. This salt speeds up the reaction by acting as a base catalyst. The most popular application of acid anhydride salt as a catalyst is in the Perkin reaction, which yields cinamic acid from benzaldehyde. To produce coumarin, acetic anhydride and the sodium salt of salicylaldehyde are also heated.
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