Any of a class of organic compounds that contain a carbonyl group (―C=O; see functional group ) in which the carbon atom is bonded to at least one hydrogen atom.
Many have characteristic odours. Oxidation (see oxidation-reduction ) of aldehydes yields acid s; reduction produces alcohol s. They participate in many chemical reaction s and readily undergo polymerization into chains containing tens of thousands of the monomer molecule. The combination of aldehydes (e.g., formaldehyde ) with other molecules results in several familiar plastics . Many aldehydes are large-scale industrial materials, useful as solvents, monomers, perfume ingredients, and intermediates. Many sugar s are aldehydes, as are several natural and synthetic hormone s and compounds such as retinal (a derivative of vitamin A , important in vision) and pyridoxal phosphate (a form of vitamin B 6 ).