How does the Cannizzaro reaction change molecules of an aldehyde?

The Cannizzaro reaction is a chemical process involving aldehydes that lack an α-hydrogen, such as benzaldehyde, when treated with a strong base like sodium hydroxide.12

In this reaction, the molecules undergo a disproportionation, or an oxidation-reduction process, where the aldehyde molecules are transformed as follows:

• Reduction: One molecule of the aldehyde is reduced to form the corresponding primary alcohol.32
• Oxidation: Another molecule of the aldehyde is oxidized to form the salt of the corresponding carboxylic acid.32

Discovered by the Italian chemist Stanislao Cannizzaro in 1853, this reaction effectively splits the aldehyde population into two different chemical products: an alcohol and an acid.12