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Carbonyl Group

Ketones, Properties Of The Carbonyl GroupOther molecules with carbonyl groups

A carbonyl group is a group of atoms that consists of a carbon atom covalently attached to an oxygen atom by a double bond: C = O. The carbon atom, to satisfy its valence of 4, must also be attached by covalent bonds to two other atoms. The simplest type of molecule that contains a carbonyl group is a ketone. Other types of molecules that contain carbonyl groups are aldehydes, acids, esters, and amides.

In many molecules that contain a carbonyl group, the other two groups of atoms are not hydrocarbon groups. Molecules like this are so different chemically that they belong to entirely different classifications. There are four major classes of molecules like this. Again, R stands for any hydrocarbon group. There is more information about these kinds of carbonyl-containing molecules in their entries in this encyclopedia.



Mark, Herman F. From Small Organic Chemicals to Large: a Century of Progress. Washington DC: American Chemical Society, 1993.

Mauskopf, Seymour H. Chemical Sciences in the Modern World. Pennsylvania: University of Pennsylvania Press, 1993.

G. Lynn Carlson


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Covalent bond

—A chemical bond formed when two atoms share a pair of electrons with each other.

Double bond

—A covalent bond consisting of two pairs of shared electrons that hold the two atoms together.

Hydrocarbon group

—A portion of a molecule containing only carbon and hydrogen atoms.


—A single particle of a substance in which the atoms join together by covalent bonds.


—The distribution of electrical forces within a molecule. There are nonpolar molecules, in which the electrical forces balance each other out, and polar ones, in which the complete molecule may still be neutral, but the electrical forces within it are not directed evenly throughout the molecule.

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