Note : In the following questions a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
Assertion : o-Nitrophenol is less soluble in water than the m- and p-isomers.
Reason : m- and p- Nitrophenols exist as associated molecules.
It is not because of the fact that m-nitrophenol and p-nitrophenol exist as associated molecules is the reason why their solubility is higher than o-nitrophenol, although the fact is correct but it is not the proper explanation which suits here.
As we discussed earlier that o-nitrophenol forms intramolecular Hydrogen bonding(bonding formed in the same molecule) due to the closeness of the –NO2 group with the –OH group. This inhibits its hydrogen bonding with water and reduces its solubility in water.
Thus we get to know that more the stable bond formed between a compound and water, more is its solubility in water.
Now, if we consider p- or m-nitrophenol we observe the formation of intermolecular hydrogen bonding(bonding with many molecules of same or different species). The intermolecular hydrogen bondings thus formed with are more stable and due to which their solubility gets increased.
