Knoevenagel Condensation - Reaction, Mechanism, and Examples are described in this article.
Knoevenagel condensation is a named reaction in organic chemistry. It is also known as modified Aldol condensation reaction. It is a C-C bond formation reaction in organic chemistry.
Key words: Nucleophilic addition, Condensation, Aldol condensation, Dehydration reaction. Named reaction.
Introduction
A Knoevenagel condensation is a nucleophilic addition of an active hydrogen compound to a carbonyl group followed by a dehydration reaction. It is a modification of the Aldol condensation. In this reaction a weakly basic amine is used as catalyst.
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| Figure : 1 Knoevenagel condensation |
Mechanism
1. A
base abstracts proton from active hydrogen component to generate enolate.
2. Nucleophilic
addition of enolate on carbonyl component (aldehyde / ketone).
3. Protonation
of alkoxide ion to form alcohol species.
4. Dehydration
of alcohol species to form carbon-carbon double bond.
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| Figure : 2 Mechanism of Knoevenagel Condensation |
The
active hydrogen component used in Knoevenagel condensation reaction can be diethyl malonate,
Meldrum's acid, ethyl acetoacetate or malonic acid, cyanoacetic acid or
nitromethane.
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| Figure: 3 Active hydrogen species |
Examples
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