Question

please explain why most diazo coupling rxns do not work well in acidic solutions

Answer 1

The mechanism of diazotization is given below Hence benzene diazonium chloride couple with phenol for diazotization. Hence phenol should be activating group which means phenol should be a better ring activator. As In basic medium the phenols H is abstracted by base. So, convert to phenoxide ion. And we no phenols’ resonating structure is less stable than phenoxide ion. So, phenoxide is better ring activator. So, in basic medium diazo coupling better as compared to acidic medium. Hence phenol should be activating group which means phenol should be a better ring activator.