The nitrophenols have completely different physical behavior based on the position of nitro group: $$ \begin{array}{c|ccc} \hline \text{Compound} & \text{Melting point} & \text{Boiling point} & \text{Water solubility at } \pu{25 ^\circ C}\\ \hline \text{2-Nitrophenol} & \pu{43-45 ^\circ C} & \pu{215 ^\circ C} & \pu{2 g/L} \\ \text{3-Nitrophenol} & \pu{89-95 ^\circ C} & \pu{278 ^\circ C} & \pu{13.5 g/L} \\ \text{4-Nitrophenol} & \pu{113-114 ^\circ C} & \pu{279 ^\circ C} & \pu{16 g/L} \\ \hline \end{array} $$ This different behavior is due to having intramolecular hydrogen bonding: Due to these intramolecular H-bonding on 2-nitrophenol, its $\ce{OH}$ group is not readily available to form a hydrogen bond with solvent water. Hence 2-nitrophenol is sparingly soluble in water while 3- and 4-nitrophenol are soluble due to intermolecular H-bonding with water. Similarly, because 3- and 4-nitrophenols contains much more intermolecular H-bonding than that of 2-nitrophenol, they have large difference in boiling and melting points than that of 2-nitrophenol (need extra energy to break intermolecular H-bonding; The intramolecular H-bonding increases the volatile nature of the molecule comparatively with their isomeric siblings that cannot have intramolecular H-bonding, thus effecting the relevant boiling points). The intramolecular H-bonding effects oppositely in the solubility in nonpolar solvents such as benzene. Compounds involved in intramolecular H-bonding (kind of chelation) become non-polar (not many interaction forces intermolecularly). As a consequent, these compounds are soluble in nonpolar solvents (oposite to only sparingly soluble in water) whereas their meta and para isomers are less soluble in non-polar solvents but more soluble in water due to intermolecular H-bonding (such as water). Boiling point of o−nitrophenol is less than boiling point of p−nitrophenol Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses Boiling point of p−nitrophenol is less than boiling point of o− nitrophenol No worries! We‘ve got your back. Try BYJU‘S free classes today! boiling point of both p− nitrophenol and o− nitrophenol are same
No worries! We‘ve got your back. Try BYJU‘S free classes today! No worries! We‘ve got your back. Try BYJU‘S free classes today! Open in App Suggest Corrections 2 |