Question

The concept that explains why $o-$nitrophenol is more volatile than $p-$nitrophenol is .

• A. resonance
• B. hyperconjugation
• C. hydrogen bonding

Answer 1

The correct option is C hydrogen bonding


In $o-$nitrophenol there exists intramolecular hydrogen bonding between the partial positively charged(${\delta }^{+}$) hydrogen of phenolic group and partial negatively charged(${\delta }^{-}$) oxygen of nitro group. Since it involves only a single molecule, the boiling point is lesser and so the compound is highly volatile.


In $p-$nitrophenol, there exists intermolecular hydrogen bonding between the partial positiviely charged(${\delta }^{+}$) hydrogen in the phenolic group of one molecule and the partial negatively charged(${\delta }^{-}$) oxygen in nitro group of another molecule. Since the hydrogen bonding involves multiple molecules, the boiling point is higher and compound is less volatile compared to $o-$nitrophenol.