These compounds exhibit significantly high diamagnetic susceptibility. Cyclic electron delocalization also results in bond length equalization, abnormal chemical shifts and magnetic anisotropies, as well as chemical and physical properties which reflect energetic stabilization. On the other hand, compounds with high paramagnetic susceptibility may be antiaromatic.
**Huckel's rule can be used to determine whether a molecule is aromatic or anti-aromatic by broadly two conditions.
* It is cyclic, planar and has continuous delocalization of π electrons (electrons in p orbitals) with or without the participation of lone pair(s)/- charge/ + charge (i.e having electrons or vacant p orbital).
* The delocalised π-electron cloud must contain a total of (4n+2)π electrons, where n is a whole number (i.e., n= 0,1,2,3 and so on) **If in the second condition there are 4n π electrons, it is anti-aromatic.
** If the first condition is not fully met,it is aliphatic.
**The term non-aromatic is applicable to both aliphatic as well as anti-aromatic. **Aromaticity is the state of stability that any molecule would thrive to achieve. These molecules are cyclic, planar and have (4n+2)π electrons continuously delocalised in a cyclic manner.