19.12 Biological Reductions
- Page ID
- 90975
Objectives
After completing this section, you should be able to
- determine whether or not a given aldehyde will undergo the Cannizzaro reaction.
- write an equation to illustrate the Cannizzaro reaction.
- identify the products formed when a given aldehyde undergoes a Cannizzaro reaction.
- write the detailed mechanism of the Cannizzaro reaction.
Make certain that you can define, and use in context, the key term below.
- Cannizzaro reaction
In 1853 Stanislao Cannizzaro discovered that the base‑induced disproportionation of an aldehyde resulted in a carboxylic acid (oxidation product) and an alcohol (reduction product).
Note that in the mechanism shown in the reading has an intermediate generated from methanal (formaldehyde) that effectively becomes a hydride (H−) donor, which reduces a second molecule of methanal to methanol.
Carbonyl reductions are a part of important biological pathways in living organisms. Recall in Section 17.4 that NADH can donate H− to reduce aldehydes and ketones. You may wish to review this section.
Cannizzaro Reaction
Exercise
Please draw the expected product(s) of the following reaction:
- Answer
Contributors and Attributions
Dr. Dietmar Kennepohl FCIC (Professor of Chemistry, Athabasca University)