Benzenes bonding consists of sideways overlap of PI bonds between carbons in the ring. due to the extensive overlapping and the PI bond not being held between two atoms the electrons are said to be delocalised and the ring is an area of low electron density. The lone pair form the O atom attached is delocalised into the ring therefore increasing the electron density of the ring, this means a dipole in the electrophile is more easily induced and therefore is more attracted to the ring. For the reaction with benzene a halogen carrier is needed (feBr3) to create Br+ to create a strong enough electrophile to react with the lower electron rich ring structure.