Question

Can phenol undergo halogenation with iodine. If so, what happens when phenol is added with iodine solution and then sodium hydroxide and warmed. This will show a negative iodoform test, but what can be observed and why?

Answer 1

The direct iodination of phenol by aqueous I₂ turned, not unexpectedout to give five different iodophenols: 2-iodophenol, 4-iodophenol, 2,6-diiodophenol, 2,4-diiodophenol and 2,4,6-triiodophenol. When
elemental iodine is treats with equivalent amounts of NaOH the solution turnes colorless, due to the formation of HOI. This strongly indicates that the same iodinating species, probably
HOI, operates in both cases.

I₂ + H₂O --> HOI + HI
HOI + phenol --> iodophenol + H₂O