Consider the following diazonium ions: I. II. III. IV. The correct increasing order of their reactivity towards azo-coupling reactions (under similar conditions) is:

Step-by-step solution

In an azo-coupling reaction, the diazonium ion acts as an electrophile. The reactivity of the diazonium ion towards coupling depends on its electrophilic character. Electron-withdrawing groups (EWGs) on the benzene ring increase the positive charge on the diazonium nitrogen, making it a stronger electrophile and thus more reactive. Conversely, electron-donating groups (EDGs) disperse the positive charge through resonance (+R effect), stabilizing the diazonium ion and making it less reactive. Let us analyze the subs