Describe the changes in the electronic properties of an phenyl ring when attached to an NO2 group or a NMe2 group when compared to a benzene ring.

NO2 is a strongly electron withdrawing group, making the ring more electrophilic (pi withdrawing).NMe2 is a strongly electron donating group, making the ring more nucleophilic (pi donating).These changes are most strongly felt on the ortho and para positions. This is due to the delocalisation of the pi electrons across the ring, a drawing of delocalistion states is needed to fully answer this question.A comment about the sigma withdrawing properties of the elctronegative nitrogen could be made, however in this case the effect if minor.