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Question 4: R groups are activating and o,p directors. The first reaction puts a nitro group (NO2) on the ring in the ortho and para positions. Para position will be preferred due to steric hindrance at the ortho position. Treatment with HCl in the presence of Sn will reduce the nitrate to amino group, NH2. Next, treatment with cold/acidic sodium nitrate, replaces the amino group with a aryldiazonium chloride. This is a positively charged N bound to the benzene ring triply bonded to another nitrogen, i.e. N2+. The Cl- ion balances this off. Finally, the CN- nucleophile replaces this N2+ group with the CN group. ...
The solution explains three problems with reaction sequences and NMR spectrums.