Why o-Nitrophenol is more steam volatile than p-Nitrophenol?
o-Nitrophenol forms intramolecular H bond whereas molecules of p-Nitrophenol get associated through intermolecular H bond. During boiling, the strong intermolecular H bonding increases the boiling point but intramolecular H bonding cannot do so.
Therefore, o-Nitrophenol is more steam volatile than p-Nitrophenol.
There are two types of hydrogen bond.One is intermolecular hydrogen bond and other is intramolecular hydrogen bond.Intermolecular H-Bond increase the melting point,boiling point of compounds having them while the intramolecular H-Bond have mostly opposite effects to that of intermolecular H-Bond(it decreases melting and boiling point).Since o-nitrophenol forms intramolecular H bond it have low Melting boiling point than p-nitrophenol(which form intermolecular H-Bond).That's why o-Nitrophenol is more steam volatile than p-Nitrophenol.