Question

Which of the following will form a tribromo derivative of phenol?

• A.
• B.
• C.
• D.

Answer 1

The correct option is D


Phenol gets ionised and forms a phenoxide ion, which is a better ortho-para directing group. Dissociation of bromine generates a bromonium ion and this happens to a larger extent in a polar solvent. In water, more $B{r}^{+}$ ions are formed which facilitate the formation of a tribrominated product where 2,4 and 6 positions are unsubstituted.
$C{S}_2$ is non-polar. So, small fractions of $B{r}^{+}$ ions would be generated and only monobrominated product would be formed.