Question

The mixture of o-nitrophenol & p-nitrophenol can be separated by

• A. Crystallisation
• B. Sublimation
• C. Distillation
• D. Steam distillation

Answer 1

The correct option is D Steam distillation

Intra-molecular hydrogen bonding is present in o-nitrophenol. This is due to the polar nature of the O-H bonds which result in the formation of hydrogen bonds within the same molecule. This intramolecular H bonding reduces water solubility and increases volatility. But in p-nitrophenol,inter molecular hydrogen bonding (between H and O atoms of two different para-nitro phenol molecules) is possible. As a result of inter molecular hydrogen bonding, p-nitrophenol undergoes association that increases the molecular weight, whereby decreasing volatility. Thus o-nitrophenol is steam distillable while p-nitrophenol is not.