Conjugation is the term used to describe an arrangement of chemical bonds in which two double bonds are separated by one single bond. Chemical structures with this configuration are very stable and can show unusual behavior during the course of a chemical reactions. This effect results from the ability of the electrons in conjugated bonds to delocalize, or spread their effect throughout the molecule. Two important examples of a conjugated system are isoprene and butadiene, both of which are important components used in the manufacture of synthetic rubber.

In molecules with conjugated bonds, saturated bonds (carbon atoms with four attached atoms) alternate with unsaturated bonds (carbon atoms with less then four attached atoms.) This bond arrangement is possible between atoms whose p-orbital electons are capable of interacting. (The term "p-orbital" describes how the electrons orbit the nucleus of the atom.) For example in 1,3-butadiene (Figure 1), the unsaturated bonds...