Consider the following compounds:
(I) 1, 2-dihydroxy benzene (II) 1, 3-dihydroxy benzene
(III) 1, 4-dihydroxy benzene (IV) Hydroxy benzene
The increasing order of boiling point of above mentioned phenols is

Options

A. I < II < III < IV
B. I < II < IV < III
C. IV < I < II < III
D. IV < II < I < III

Answer

C

Explanation

IV lt I lt II lt III
1,4-Dihydroxy benzene shows the highest boiling point among the given compounds because it forms strong intermolecular hydrogen bond (it does not form intramolecular H-bonding).
Intermolecular H-bonding
The order of H-bonding in o-, m-, and p-isomers of a compounds is given below:
Intermolecular H-bonding o-lt m-lt p-isomers
Intramolecular H-bonding o- gt m- gt p-isomers
Hydroxybenzene does not form a chain of bonding. Hence, intermolecular H-bond is stronger than intramolecular H-bond. Consequently, the stability of 1,4-dihydroxy is highest. Hence its boiling point is highest.