# How does the solvent determine whether mono- or tribromination of phenol occurs?

In phenol, the $-\ce{OH}$ group activates the benzene ring towards electrophilic substitution. But why is it that the electrophilic bromination of phenol gives trisubstitution (forming 2,4,6-tribromophenol) when aqueous bromine is used, but monosubstitution (either 2- or 4-bromophenol) when a $\ce{CCl4}$ solution of bromine is used? How does the solvent control the extent of bromination?

Related but does not explain completely: How do we know whether we will get a mono substituted or tri-substituted product during electrophilic aromatic substitution?

$$\ce{PhOH + H2O <<=> PhO- + H3O+}$$
1. The concentration of $\ce{Br^+}$ is higher in water than in $\ce{CCl4}$ making the reaction faster in water.
2. The dielectric constant of water is much greater than that of $\ce{CCl4}$, so the former solvent will better stabilize the charged intermediate, again accelerating the reaction.