Benzene
The simplest aromatic hydrocarbon, a planar regular hexagon of six sp² carbons with a delocalised pi cloud.
Formula / equation
C₆H₆
Unit
Dimensionless
In depth
All six C–C bonds are identical at 139 pm, intermediate between single and double, and the resonance energy of about 150 kJ/mol makes the ring resistant to addition. Kekulé's alternating-bond proposal was superseded by the delocalised description now drawn as a circle.
Examples in the real world
The parent of countless dyes, drugs and polymers; a known carcinogen restricted to closed industrial systems.