The Cannizzaro reaction, named after its discoverer Stanislao Cannizzaro, is a chemical reaction that involves the base-induced disproportionation of an aldehyde lacking a hydrogen atom in the alpha position.[1][2] Cannizzaro first accomplished this transformation in 1853, when he obtained benzyl alcohol and benzoic acid from the treatment of benzaldehyde with potash (potassium carbonate).
The oxidation product is a carboxylic acid and the reduction product is an alcohol. For aldehydes with a hydrogen atom alpha to the carbonyl, i.e. RCHR'CHO, the preferred reaction is an aldol condensation, originating from deprotonation of this hydrogen. Reviews have been published.[3]
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A special condition is the crossed Cannizzaro reaction. This variation is more common these days because the original Cannizzaro reaction yields a mixture of alcohol and carboxylic acid. For example any aldehyde with no alpha hydrogens can be reduced when in the presence of formaldehyde. Formaldehyde is oxidized to formic acid and the corresponding alcohol is obtained in a high yield although the atom economy is still low.
Cannizzaros`s reaction is also performed with Benzaldehyde in the presence of concentrated Sodium Hydroxide to give Sodium Benzoate (C6H5COONa) and Benzal Alcohol (C6H5CH2OH).
A solvent-free reaction has been reported involving mixing 2-chlorobenzaldehyde with potassium hydroxide in a mortar and pestle [4]:
SHOULD BE CORRECTED