Understanding Aromaticity and Its Rules

Aromaticity — In-Depth but Concise Aromatic molecules are unusually stable because their π

electrons are delocalized around a ring, lowering the molecule’s energy. A molecule is aromatic

only if ALL four conditions are met: Cyclic – electrons must be able to circulate.

Planar – p orbitals must overlap; nonplanar rings lose overlap. Fully conjugated – every atom in

the ring must have a p orbital (sp² or sp). 🚫 Even ONE sp³ atom makes the ring

nonaromatic. Hückel’s Rule – must have 4n + 2 π electrons (2, 6,

10, 14…). π-Electron Counting Each double bond = 2 π electrons

Lone pairs count ONLY if they are in a p orbital Charges matter: Negative charge