KNOEVENAGEL CONDENSATION Meaning and
Definition
-
Knoevenagel condensation is a versatile organic reaction that involves the formation of a carbon-carbon double bond through the condensation of an aldehyde or a ketone with an active methylene compound. It is named after the German chemist Emil Knoevenagel, who first developed this reaction in the late 19th century.
In this reaction, the aldehyde or ketone reacts with a compound that possesses at least one methylene group adjacent to a carbonyl group, such as malonic ester, ethyl cyanoacetate, or a 1,3-dicarbonyl compound. The reaction takes place under basic conditions, usually with the addition of a strong base, such as sodium ethoxide or potassium tert-butoxide.
The reaction proceeds through nucleophilic addition of the resonance-stabilized enolate intermediate formed from the active methylene compound to the carbonyl group of the aldehyde or ketone. This leads to the formation of an intermediate, which subsequently undergoes an elimination of a water or an alcohol molecule. This elimination process results in the formation of a carbon-carbon double bond and the regeneration of the base catalyst.
Knoevenagel condensation is widely used in organic synthesis for the construction of complex molecules. It offers a convenient method for the synthesis of α,β-unsaturated carbonyl compounds, which are important intermediates in the synthesis of pharmaceuticals, natural products, and other valuable compounds. Moreover, this reaction can be extended to the synthesis of heteroatom-containing compounds by employing suitable starting materials.
Etymology of KNOEVENAGEL CONDENSATION
The word "knoevenagel condensation" is named after the German chemist Emil Knoevenagel. Emil Knoevenagel (1865-1921) was a prominent organic chemist who made significant contributions to the field of organic synthesis. He developed the knoevenagel condensation reaction in the late 19th century, which involves the condensation of an aldehyde or ketone with an active methylene compound (a compound with a methylene group bonded to a carbonyl group) in the presence of a base, resulting in the formation of an α,β-unsaturated carbonyl compound. As a tribute to his pioneering work on this reaction, it has been named after him.
