Home >
Community >
How does the solvent determine whether mono- or tribromination of phenol occurs?
Upvote
23
Downvote
+ Solvents
+ Biochemistry
+ Phenols
Posted by
Mike Hatlee
How does the solvent determine whether mono- or tribromination of phenol occurs?
In aqueous medium, phenol is deprotonated to a certain extent, forming the phenoxide ion in which the ortho and para positions are even more activated than in phenol itself. Hence, trisubstitution occurs here.
$$\ce{PhOH + H2O <<=> PhO- + H3O+}$$
In an organic solvent, phenol is not deprotonated and monosubstitution tends to occur.
ron also pointed out in a comment that:
The concentration of $\ce{Br^+}$ is higher in water than in $\ce{CCl4}$ making the reaction faster in water.
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.
In aqueous medium, phenol is deprotonated to a certain extent, forming the phenoxide ion in which the ortho and para positions are even more activated than in phenol itself. Hence, trisubstitution occurs here.
$$\ce{PhOH + H2O <<=> PhO- + H3O+}$$
In an organic solvent, phenol is not deprotonated and monosubstitution tends to occur.
ron also pointed out in a comment that:
The concentration of $\ce{Br^+}$ is higher in water than in $\ce{CCl4}$ making the reaction faster in water.
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.
In aqueous medium, phenol is deprotonated to a certain extent, forming the phenoxide ion in which the ortho and para positions are even more activated than in phenol itself. Hence, trisubstitution occurs here.
$$\ce{PhOH + H2O <<=> PhO- + H3O+}$$
In an organic solvent, phenol is not deprotonated and monosubstitution tends to occur.
ron also pointed out in a comment that:
In aqueous medium, phenol is deprotonated to a certain extent, forming the phenoxide ion in which the ortho and para positions are even more activated than in phenol itself. Hence, trisubstitution occurs here.
$$\ce{PhOH + H2O <<=> PhO- + H3O+}$$
In an organic solvent, phenol is not deprotonated and monosubstitution tends to occur.
ron also pointed out in a comment that:
More
VOTE