Question

Select the compound from the following that will show intramolecular hydrogen bonding.

• A. \( \text{H}_2\text{O} \)
• B. \( \text{NH}_3 \)
• C. \( \text{C}_2\text{H}_5\text{OH} \)
• D.

  

Answer 1

The Correct Option is D

To determine which compound will show intramolecular hydrogen bonding, we need to understand the concept of intramolecular hydrogen bonding. Intramolecular hydrogen bonding occurs within a single molecule when a hydrogen atom bound to a highly electronegative atom such as oxygen, nitrogen, or fluorine forms a hydrogen bond with a lone pair of electrons from another electronegative atom within the same molecule. This type of bonding often leads to the formation of a five or six-membered ring.

Given the options: 

• \(\text{H}_2\text{O}\): Water molecules exhibit intermolecular hydrogen bonding between different molecules, not intramolecular.
• \(\text{NH}_3\): Ammonia forms hydrogen bonds with other molecules of ammonia rather than intramolecular hydrogen bonds.
• \(\text{C}_2\text{H}_5\text{OH}\): Ethanol has the ability to form hydrogen bonds, but these are not intramolecular. The hydrogen of the hydroxyl group forms hydrogen bonds with the oxygen of another ethanol molecule, which is intermolecular bonding.
• The fourth option includes an image of the compound:

The compound depicted in the image is typically salicylaldehyde or orthonitrophenol, which has a hydroxyl group (–OH) and another electronegative group such as an aldehyde (–CHO) or nitro (–NO₂) on adjacent positions. In such compounds, a hydrogen bond can form between the hydrogen atom of the hydroxyl group and the lone pair of electrons on the electronegative atom of the adjacent group, resulting in intramolecular hydrogen bonding.

Conclusion: The depicted compound in the image is correctly identified as having the potential for intramolecular hydrogen bonding. Hence, the correct answer is the compound represented by the image with data-src-id="67347e092f20741705a5c770".

Answer 2

Intramolecular hydrogen bonding occurs when a hydrogen atom within a molecule forms a hydrogen bond with another electronegative atom (e.g., oxygen, nitrogen) present within the same molecule. This bonding is typically observed when the two groups are positioned such that they can interact effectively within the molecule.
Analysis of Each Option:
Option (1):H$_2$O: Water molecules exhibit strong intermolecular hydrogen bonding rather than intramolecular hydrogen bonding.
Option (2): NH$_3$: Ammonia also forms intermolecular hydrogen bonds due to the presence of nitrogen with lone pairs, but it does not exhibit intramolecular hydrogen bonding.
Option (3): C$_2$H$_5$OH (ethanol): Ethanol primarily forms intermolecular hydrogen bonds between different molecules rather than within the same molecule.
Option (4): The compound depicted is ortho-nitrophenol. In ortho-nitrophenol, the hydroxyl (OH) group and the nitro (NO$_2$) group are positioned such that intramolecular hydrogen bonding occurs between the hydrogen atom of the OH group and one of the oxygen atoms of the NO$_2$ group. This interaction stabilizes the molecule and reduces its tendency to form intermolecular hydrogen bonds.
Conclusion:
Ortho-nitrophenol (Option 4) exhibits intramolecular hydrogen bonding.