Benzenediazonium salts on reaction with phenol gives?

Diazonium ions are present in solutions such as benzenediazonium chloride solution. They contain an -N₂⁺ group. In the case of benzenediazonium chloride, this is attached to a benzene ring.

Benzenediazonium chloride looks like this:

In this set of reactions of the diazonium ion, the -N₂⁺ group is replaced by something else. The nitrogen is released as nitrogen gas.

Substitution by an -OH group

To get this reaction, all you need to do is warm the benzenediazonium chloride solution. The diazonium ion reacts with the water in the solution and phenol is formed - either in solution or as a black oily liquid (depending on how much is formed). Nitrogen gas is evolved.

This is the same reaction that you get if you react phenylamine with nitrous acid in the warm. The diazonium ion is formed first and then immediately reacts with the water in the solution to give phenol.

Substitution by an iodine atom

This is a good example of the use of diazonium salts to substitute things into a benzene ring which are otherwise quite difficult to attach. (That''s equally true of the previous reaction, by the way.)

If you add potassium iodide solution to the benzenediazonium chloride solution in the cold, nitrogen gas is given off, and you get oily droplets of iodobenzene formed.

There is a simple reaction between the diazonium ions and the iodide ions from the potassium iodide solution.

Coupling reactions of diazonium ions