Cannizzaro Reaction: Laboratory Application
For preparative purposes, the Cannizaro reaction as such is rather unimportant, because one equivalent of aldehyde generates only half an equivalent each of acid and alcohol. Therefore, the reduction of aldehydes to alcohols in the laboratory is carried out preferably using the crossed-Cannizaro reaction. In this reaction, formaldehyde is reacted with another aldehyde. Lacking an electron-pushing alkyl group, formaldehyde is the most reactive aldehyde as a nucleophile. The hydoxyl ion is added to formaldehyde which subsequently transfers a hydride ion to the other aldehyde. The final result is the formation of formic acid and an alcohol corresponding to the second aldehyde.