question_answer

At low temperature phenol reacts with \[B{{r}_{2}}\] in \[C{{S}_{2}}\] to form [MP PET 1991; CPMT 1981; MP PMT 1990; IIT 1982; RPMT 2000]

A)                 m-bromophenol             

B)                 o-and p-bromophenol

C)                 p-bromophenol               

D)                 2, 4, 6-tribromophenol

Correct Answer: B

Solution :

               In presence of non-polar solvent \[(C{{S}_{2}})\] the ionization of phenol is suppressed. The ring is slightly activated and hence mono substitution occurs.                    On the other hand with \[B{{r}_{2}}\] water phenol forms 2, 4, 6-tribromo phenol. In aqueous solution phenol ionizes to give phenoxide ion. Due to the presence of negative charge on oxygen the benzene ring is highly activated and hence trisubstituted product is obtained.