We add 1 equivalent of $\ce{KCN}$ followed by catalytic reduction via Lindlar's reagent $(\ce{H2}/\ce{Pt})$ to 4-chlorobenzyl chloride (1).
Verify whether the product (P) obtained will undergo an N−N coupling reaction with a diazonium salt or not.
According to me, it should because I find no valid reason as to why it shouldn't. The product P that I obtained was 4-chlorobenzylamine (2):
But the book mentions that it won't. That made me wonder if there are some amines that don't participate in coupling reactions, or is it because of something else.