explain
aldol condensation and cannizzaro reaction
Answers
An aldol condensation is a condensation reaction in organic chemistry in which an enol or an enolate ion reacts with a carbonyl compound to form a β-hydroxyaldehyde or β-hydroxyketone (an aldol reaction), followed by dehydration to give a conjugated enone.
Aldol condensations are important in organic synthesis, because they provide a good way to form carbon–carbon bonds.[1] For example, the Robinson annulation reaction sequence features an aldol condensation;[1] the Wieland–Miescher ketone product is an important starting material for many organic syntheses.[2] Aldol condensations are also commonly discussed in university level organic chemistry classes as a good bond-forming reaction that demonstrates important reaction mechanisms.[3][4][5] In its usual form, it involves the nucleophilic addition of a ketone enolate to an aldehyde to form a β-hydroxy ketone, or "aldol" (aldehyde + alcohol), a structural unit found in many naturally occurring molecules and pharmaceuticals.[6][7][8]
The name aldol condensation is also commonly used, especially in biochemistry, to refer to just the first (addition) stage of the process—the aldol reaction itself—as catalyzed by aldolases. However, the aldol reaction is not formally a condensation reaction because it does not involve the loss of a small molecule.
The reaction between an aldehyde or ketone having an alpha-hydrogen with an aromatic carbonyl compound lacking an alpha hydrogen is called the Claisen–Schmidt condensation. This reaction is named after two of its pioneering investigators Rainer Ludwig Claisen and J. G. Schmidt, who independently published on this topic in 1880 and 1881.[9][10][11]An example is the synthesis of dibenzylideneacetone. Quantitative yields in Claisen–Schmidt reactions have been reported in the absence of solvent using sodium hydroxide as the baseand plus benzaldehydes.[12] Because the enolizeable nucleophilic carbonyl compound and the electrophilic carbonyl compound are two different chemicals, the Claisen–Schmidt reaction is an example of a crossed aldol process.
