Resonance (chemistry) - Representations

Representations

The ozone molecule is represented by two resonance structures. In reality the two terminal oxygen atoms are equivalent and the hybrid structure is drawn on the right with a charge of -1/2 on both oxygen atoms and partial double bonds with a full and dashed line and bond order 1.5.

In benzene the two cyclohexatriene Kekulé structures first proposed by Kekulé are taken together as contributing structures to represent the total structure. In the hybrid structure on the right the dashed hexagon replaces three double bonds, and represents six electrons in a set of three molecular orbitals of π symmetry, with a nodal plane in the plane of the molecule.

The allyl cation has two contributing structures with a positive charge on the terminal carbon atoms. In the hybrid structure their charge is +1/2. The full positive charge can also be depicted as delocalized among three carbon atoms.

In furan a lone pair of the oxygen atom interacts with the π orbitals of the carbon atoms. The curved arrows depicture the move of delocalized π electrons, which results in different contributors.