Question

Intramolecular hydrogen bonding is found in

• A. o-nitrophenol
• B. m-nitrophenol
• C. p-nitrophenol
• D. phenol

Hint:

Intramolecular hydrogen bonding results in a stable, closed-ring structure within the molecule.

Answer 1

The Correct Option is A

Step 1: {Intramolecular Hydrogen Bonding}
In o-nitrophenol, the hydrogen of the \({O-H}\) group and the oxygen of the nitro group form intramolecular hydrogen bonding producing a six-membered ring structure. In m-nitrophenol, p-nitrophenol, and phenol, intermolecular hydrogen bonding is present. Hence, the correct answer is (A).

Answer 2

Step 1: Understand what is intramolecular hydrogen bonding
Intramolecular hydrogen bonding occurs when a hydrogen atom forms a hydrogen bond within the same molecule, typically between a hydrogen attached to an electronegative atom (like O–H or N–H) and a lone pair on another electronegative atom within the same molecule.
This bonding results in a six-membered or five-membered pseudo-ring structure and reduces the molecule's ability to form hydrogen bonds with water, affecting properties like boiling point and solubility.

Step 2: Analyze the structure of o-nitrophenol
o-Nitrophenol has a hydroxyl group (-OH) and a nitro group (-NO₂) positioned ortho (adjacent) to each other on a benzene ring.
This proximity allows the hydrogen of the –OH group to form a hydrogen bond with one of the oxygen atoms of the –NO₂ group within the same molecule.
This is a classic case of intramolecular hydrogen bonding.

Step 3: Compare with other isomers or compounds
- m-Nitrophenol (meta position) and p-Nitrophenol (para position) cannot form intramolecular H-bonds due to the spatial distance between –OH and –NO₂ groups.
- They typically exhibit intermolecular hydrogen bonding instead.

Step 4: Final Answer
Intramolecular hydrogen bonding is found in:
o-nitrophenol