Question

The correct order of boiling point of the compounds is as follows:
A.
B.
C.
D.

1.C > A > D > B
2.A > B > C > D
3.D > A > B > C
4.A > B > D > C

Answer 1

The boiling points of organic compounds are affected by different factors and among them the major ones include the intermolecular forces of attraction and the molecular weights of the compounds.

Complete step-by-step answer: Among the given compounds, there are three isomers of nitrophenol, the para-nitrophenol, the ortho-nitrophenol, and the meta-nitrophenol and only phenol. The boiling points of the isomers are affected by hydrogen bonding as the molecular weights of all are the same. The boiling point of para-nitrophenol is the highest followed by the meta-nitrophenol and finally the ortho-nitrophenol. This is due to the intermolecular hydrogen bonding in para-nitrophenol which is absent in both meta-nitrophenol and ortho-nitrophenol. This prevents the molecule from boiling faster.
The boiling point of phenol is lower than that of meta-nitrophenol and para-nitrophenol due to their higher molecular weight but it is higher than that of o-nitrophenol due to the presence of intermolecular hydrogen bonding among its molecules as well.

Hence, the correct order of bonding is as follows: A > B > C > D, and the correct answer is option 2.

Note: Phenol is a ortho, para orienting compound and when it is treated with a concentrated solution of nitric acid along with sulphuric acid, then it results in the formation of the para-nitrophenol and the ortho-nitrophenol. To get the meta-nitrophenol, the ortho and para positions need to be blocked first and then treated with the concentrated acid mixture.