Question
Thu January 27, 2011 By: Pratik Sethi

GIVE REASON, WHY p-bromo phenol is a major product while o-bromophenol is a minor product when phenol is treated with bromine in carbon tetrachloride. dont we get m-nitrophenol in this reaction?

Expert Reply
Thu January 27, 2011
Dear Student
 
In a non-polar solvent CCL4,  the ionization of phenols is greatly supprressed. So, the oxygen of OH group donates electrons to benzene ring only to a small extent and consequently the ring is activated only slighlty and hence only monosubstitution occurs. further because of steric hindrance at ortho-position the para substittuion product usually predominates.
 
Meta substitution does not occur because –OH  group is a +R group and tend to increase the electron density only on the ortho and para carbon making these positions vulnerable to the electrophilic attack.
 
We hope that clarifies your query.
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Team
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