What is a delocalized bond?

A delocalized bond, also known as a delocalized electron bond or a resonance bond, is a type of chemical bond in which electrons are not localized between two specific atoms but are instead spread out or shared over multiple atoms within a molecule or ion. This concept is commonly associated with organic chemistry and is particularly important in understanding the behavior of certain molecules with alternating or conjugated double bonds.

In a delocalized bond, the electrons are not confined to a single pair of atoms but are free to move or be shared among several atoms. This sharing of electrons over a larger region of the molecule results in increased stability and unique properties. Delocalized bonds are often represented using resonance structures or resonance forms, which are different Lewis structures that describe the possible locations of the shared electrons.

A classic example of a molecule with delocalized bonds is benzene (C6H6). In benzene, there are three double bonds represented by alternating single and double bonds in its Lewis structure. However, experimental evidence shows that the electrons in the double bonds are not localized between specific pairs of carbon atoms but are distributed evenly across all six carbon atoms in a ring. This gives benzene its unique stability and reactivity.

Delocalized bonds are also found in other organic molecules with conjugated systems, such as polyenes, aromatic compounds, and some resonance-stabilized ions. They play a crucial role in the electronic structure and chemical properties of these compounds.