Double bond

Double Bond

A double bond in chemistry is a chemical bond between two chemical elements involving four bonding electrons instead of the usual two. The most common double bond occurs between two carbon atoms and can be found in alkenes. Many types of double bonds exist between two different elements. For example, in a carbonyl group with a carbon atom and an oxygen atom. Other common double bonds are found in azo compounds (N=N), imines (C=N), sulfoxides (S=O), and peroxides (O=O). In ethene (ethylene), the double bond is the source of the compound's useful reactivity.

Structure and bonding

Double bonds are shorter than single bonds because p-orbital overlap is maximized. With regard to the bond order, double bonds are stronger than single bonds, but they are less stable. This increased strength and decreased stability can be explained in terms of electronic structure. In molecules with double bonds, p-orbital overlap creates bonding over a larger spatial volume than is available in a simple single bond. As a consequence, electrons in double bonds are more delocalized than in single bonds.

Double bonds in alkenes

The simplest example of a double bond is found in ethene (also known as ethylene, H2C=CH2). In ethene, the double bond is formed from the overlap of the sp2 orbitals of the two carbon atoms, and from the overlap of the p orbitals of the two carbon atoms.

Double bonds between different elements

Double bonds can also occur between different elements. One of the most common types of double bond is that found in carbonyl groups (C=O). Other common types of double bonds are those in azo compounds (N=N), imines (C=N), sulfoxides (S=O), and peroxides (O=O).

See also

• Chemical bond
• Alkene
• Carbonyl group
• Azo compound
• Imine
• Sulfoxide
• Peroxide

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