Consider the three aromatic molecules (P, Q and R) whose structures have been given below : The correct order regarding the reactivity of these compounds with Ph-N NCl^ (-) _ (+) under optimum but slightly acidic medium is :

Step-by-step solution

The reaction of the given aromatic compounds with benzenediazonium chloride ( Ph-N₂^+ Cl^- ) is an azo coupling reaction, which is a type of electrophilic aromatic substitution. The electrophile, the diazonium ion ( Ph-N₂^+ ), is a weak electrophile and requires a strongly activated aromatic ring to undergo coupling. The reactivity of the ring depends on its electron density, which is enhanced by the +M (mesomeric) effect of the -NMe₂ group. 1. In molecule P (N,N-dimethylaniline), the -NMe₂ group is coplanar with t