Question

Intramolecular hydrogen bond is not present in:
A. o-fluoro phenol
B. salicylaldehyde
C. o-nitrophenol
D. p-nitrophenol

Answer 1

For solving this question, we need to understand the difference between intermolecular and intramolecular hydrogen bonding. Intermolecular hydrogen bonds are formed when the H atom and electronegative atoms like O, N, F, Cl, etc form a bond with different molecules. Whereas, intramolecular hydrogen bonding is formed when both H atoms and electronegative atoms form bonds from the same molecule.
Complete step by step answer: As we know that, there are two types of hydrogen bonding is possible i.e. intermolecular hydrogen bond and intramolecular hydrogen bonds. We can define intermolecular hydrogen bonding as a bond formed between two different molecules of the same and different compounds. For example: HF molecule. And intramolecular hydrogen bonding can be defined as the bond formed when the H atom is bonded to an electronegative atom of the same molecule.
To solve this question, first we will draw the chemical compounds of all the four options mentioned above:


Now, we will refer to each chemical compound and we know that in p-nitrophenol, the $OH$ and $N{O_2}$ ​ are far apart from each other and are not able to form an intramolecular H-bond.
So, p-nitrophenol (option D) will not form an intramolecular hydrogen bond.

Note: From this question, we need to keep in mind that intramolecular forces are stronger than covalent bonds. As covalent bonds involve actual sharing of electrons because the molecule forming intramolecular hydrogen bonding contains two groups. Here, one group contains a hydrogen atom that links to the highly electronegative atom and the other group contains a highly electronegative atom that is linked to a less electronegative atom.