Synthesis of aromatics
1. On the basis of electronic theory, explain the following observations:

a. The -N(CH3)2 group is an ortho, para director, and strongly activates the ring, whereas the -N(CH3)3 group is a meta director and deactivates the ring toward electrophilic substitution.
b. The -NO2 group is a meta director, and its presence on the ring makes electrophilic substitution more difficult as compared with the -NH2 group, which is an ortho, para director.

2. Devise a suitable reaction sequence in which each of the following compounds can be prepared from benzene in good yield. Assume ortho and para isomers are separate from one another, and use any other reagents you desire.
a. p-Bromoisopropylbenzene
b. m-Nitrobenzenesulfonic acid
c. p-Tert-butylbenzenesulfonic acid
d. m-Xylene