Question

Strong intra-molecular hydrogen bond is present in:

• A. water
• B. hydrogen fluoride
• C. o-cresol
• D. o-nitrophenol
• E. ammonia

Hint:

In molecules with both a hydroxyl group and an electronegative group (such as nitro), strong intra-molecular hydrogen bonds are often observed, especially when the donor and acceptor groups are positioned near each other within the same molecule.

Answer 1

The Correct Option is D

In order to form a strong intra-molecular hydrogen bond, the hydrogen bonding donor (such as an -OH group) must be in close proximity to a highly electronegative atom (such as oxygen or nitrogen), with the donor and acceptor groups positioned for effective hydrogen bonding within the same molecule.
Now, let's evaluate each compound:
- Water (A): Water molecules form hydrogen bonds with other water molecules, but it does not form a strong intra-molecular hydrogen bond within a single molecule.
- Hydrogen fluoride (B): Hydrogen fluoride also forms intermolecular hydrogen bonds with other molecules of HF but does not form a strong intra-molecular hydrogen bond.
- o-Cresol (C): o-Cresol has the possibility for intramolecular hydrogen bonding, but it is not as strong as in o-nitrophenol.
- o-Nitrophenol (D): In o-nitrophenol, the hydroxyl group (-OH) and the nitro group (-NO2) are positioned in such a way that they can form a strong intra-molecular hydrogen bond, making it the correct answer.
- Ammonia (E): Ammonia does not form intra-molecular hydrogen bonds.
Thus, the correct answer is option (D), o-nitrophenol, where strong intra-molecular hydrogen bonding occurs between the -OH and -NO2 groups.
Thus, the correct answer is option (D), o-nitrophenol.