Describe the features of a benzene ring that define its reactivity. How does phenol differ from this?

The six carbon atoms in benzene are arranged in a planar ring, with one hydrogen atom bonded to each carbon. Each carbon atom has 4 valence electrons, and uses three of them to form single bonds with the two adjacent carbon atoms and one hydrogen atom. The remaining electron exists in a p orbital which is perpendicular to the plane of the molecule. The six singly-occupied carbon p orbitals in the benzene ring overlap sideways above and below the plane of the molecule, producing a pi ring of six delocalised electrons. The delocalised electrons make benzene more reactive than if it had three localised double bonds instead. Phenol has a similar structure to benzene, with an -OH hydroxyl group on to one of the carbons in the ring instead of a hydrogen atom. The oxygen atom has six valence electrons, and uses two of them to form two single bonds (one to a hydrogen and one to a carbon), so it has two lone pairs of electrons. One of these lone pairs is added into the delocalised benzene ring, so that it becomes a 'lollipop' shape.