question_answer 117)

   (a) Name the starting material used in the industrial preparation of phenol. (b) Write complete reaction for the bromination of phenol in aqueous and non aqueous medium. (c) Explain why Lewis acid is not required in bromination of phenol.

Answer:

                  (a) Cumene. For details refer to sec. 11.6, page 11/19. (b) Refer to sec. 11.8, pages 11/37-11/38. (c) In bromination of benzene, Lewis acid is used to polarize  to form the reactive electrophile,  In case of phenol, Lewis acid is not required because the O-atom of phenol itself polarizes the Br2 molecule to form ions. Further, +R-effect of OH group makes phenol highly activated towards electrophilic substitution reactions.