- The phenomenon of delocalization of pi electrons in a conjugated system is called resonance.
- This delocalization of pi electrons in the molecule decresases the energy of molecule and increases the stability of molecules.
- The decrease in the energy i.e potential energy due to decolazation of pi electrons is known as resonance or also know as mesomeric effect.
- In resonance the molecule can be represented by more than one structure called as resonating structure which increases the stability.
- There are different structute , they are called resonating structure or canonical structure or contributing structures.
There are the followings conditions for resonance :
- Shifting of pi electrons occurs.
- nuclei remains same in all structures.
- charged structures are less stable than uncharged.
- energy content will be almost same.
- more the number of resonating structure more will be the stability.
Difference between Resonance and Mesomeric effect
- Resonance involves all types of electron displacements.
- While the mesomeric effect noticable only in those cases where a multiple bond is in conjugated with a multiple bond or electron pair.