Q.Identify A to E in the following sequence of reactions: toluene --CH3Cl/AlCl3--> A (major product) --HNO3/H2SO4--> B --Sn/HCl--> C --NaNO2/HCl--> D --CuCN--> E.

Step 1. Toluene + CH3Cl/AlCl3 is Friedel-Crafts alkylation: the existing methyl group is ortho/para-directing, and the LESS sterically hindered PARA product dominates, giving A = p-xylene (1,4-dimethylbenzene) as the major product.

Step 2. A + HNO3/H2SO4 nitrates the ring: both methyl groups are ortho/para-directing and reinforce each other at the position between them, giving B = 2-nitro-1,4-dimethylbenzene (a mononitro-p-xylene).

Step 3. B + Sn/HCl reduces the nitro group to the primary amine, giving C = 2,5-dimethylaniline (the amine, now the reference point for numbering, sits with one methyl ortho and one methyl meta/para relative to it -- renumbered as 2,5-dimethylaniline with -NH2 at C1). …

Walk the five-step chain one named reaction at a time -- Friedel-Crafts alkylation (para-selective), nitration (both methyls reinforcing one site), nitro reduction, diazotisation, then Sandmeyer cyanation -- renumbering th …

• Forgetting that Sandmeyer with CuCN installs -CN in place of the diazonium group (releasing N2), and instead treating CuCN as simply a copper-based REDUCING agent (as in the hydrogen-replacement reaction) -- CuCN specif …