Resonance is very common and significant feature of many organic molecules. Due to its presence, there is a pronounced influence on the structure, chemical reactions and physical properties of such molecules.
**Resonance energy is defined as the energy difference between the most stable resonating structure and the resonance hybrid structure.
** Resonance increases stability by increasing the bonding between adjacent atoms and by distributing charge over a greater number of atoms.
**A cross-conjugated system has a double-bonded unit single-bonded to one of the middle atoms of another conjugated chain. On the other hand, a normal conjugated system such as a polyene typically has alternating single and double bonds along consecutive atoms.
**Conjugation is broken completely by the introduction of saturated (sp3) carbon: