Explain the reasons for the changes in reactivity of Phenol, Benzene and MethylBenzene

The changes in reactivity are due to the electron donating/withdrawing properties of the substituted groups. For example the OH group in Phenol is electron donating. This means the electron density of the delocalised ring will have increased, meaning it can polarise bonds more readily. MethylBenzene is less reactive as the Methyl group is electron withdrawing, this means the electron density of the delocalised ring will have decreased, hence decreasing the reactivity. This makes it less reactive than Benzene.