Chemical compound

Print Cite Share MoreWRITTEN BYRichard O.C. NormanSee All ContributorsRector, Exeter College, University of Oxford. Professor of Chemistry, University of York, England, 1956–87. Author of Principles of Organic Synthesis.See Article History

Chemical compound, any substance composed of identical molecules consisting of atoms of two or more chemical elements.

Reaction types

The electronic features of functional groups are responsible for the types of reactions that are characteristic of each group (see above Functional groups). Because there is a great deal of similarity in the electronic characteristics of the different functional groups, there is a corresponding similarity in the types of reaction that different groups undergo. Just as the properties of the multitude of organic compounds are made more comprehensible by considering the reactions of a specific functional group, so too can the plethora of organic reactions be made more understandable by categorization into common types of chemical reaction, such as substitution, elimination, addition, hydrolysis, condensation, and acid-base and oxidation-reduction reactions.

Organic compounds

In general, organic compounds are substances that contain carbon (C), and carbon atoms provide the key structural framework that generates the vast diversity of organic compounds. All things on the Earth (and most likely elsewhere in the universe) that can be described as living have a crucial dependence on organic compounds. Foodstuffs—namely, fats, proteins, and carbohydrates—are organic compounds, as are such vital substances as hemoglobin, chlorophyll, enzymes, hormones, and vitamins.

Inorganic compounds

Inorganic compounds include compounds that are made up of two or more elements other than carbon, as well as certain carbon-containing compounds that lack carbon-carbon bonds, such as cyanides and carbonates. Inorganic compounds are most often classified in terms of the elements or groups of elements that they contain. Oxides, for example, can be either ionic or molecular. Ionic oxides contain O²⁻ (oxide) ions and metal cations, whereas molecular oxides contain molecules in which oxygen (O) is covalently bonded to other nonmetals such as sulfur (S) or nitrogen (N).