Question

Phenol gives tribromophenol when treated with bromine in aqueous solution but only $o$ - and $p$ -bromophenols in $CCl _{4}$ solution because

• A. in aqueous solution the bromine is ionised.
• B. in aqueous solution, phenol exists in equilibrium with phenoxide ion which has more activating effect.
• C. In $CCl _{4}$, the electrophilicity of $Br _{2}$ increases.
• D. In $CCl _{4}$, the other positions of benzene rings are blocked by the solvent.

Answer 1

Answer: (B)

In phenol- $OH $ group has activating and $o, p$ -directing effect, in aqueous solution due to the presence of phenoxide ion this effect is enhanced and $2,4,6$ -tribromophenol is obtained on the reaction with bromine. But in presence of non-polar $\left( CCl _{4}\right)$ medium, the activity of phenol is decreased and only ortho and para-bromophenols are obtained.