In a set of reactions p-nitrotoluene yielded a product E. The product E would be:

In the first step, bromine gets substituted on the ortho position to CH3. On reaction with Sn/HCl, NO2 gets reduced to NH2. In the third step, NH2 becomes N+2Cl−. The last step is the Gattermann reaction in which N+2Cl− becomes bromine.