Which of the following carbonyl oxygen will form strongest hydrogen bond with `H_(2)O` molecule?

Options

A.
B.
C.
D.

Answer

To determine which carbonyl oxygen will form the strongest hydrogen bond with an H₂O molecule, we need to analyze the stability of the negative charge on the oxygen atom in each given compound. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand the Concept of Hydrogen Bonding
Hydrogen bonding occurs when a hydrogen atom covalently bonded to a highly electronegative atom (like oxygen) interacts with another electronegative atom. In this case, we are looking at the interaction between the carbonyl oxygen and the hydrogen atoms of water (H₂O).

### Step 2: Analyze Each Compound
We have four options (let's denote them as A, B, C, and D). We will analyze the stability of the negative charge on the carbonyl oxygen for each compound.

#### Option A:
- When the carbonyl bond breaks, the oxygen will carry a negative charge.
- The structure is cyclic and planar but is anti-aromatic due to having 4 pi electrons.
- Anti-aromatic compounds are unstable, which means the negative charge on oxygen is not stabilized.
- **Conclusion**: This will not form the strongest hydrogen bond with water.

#### Option B:
- When the carbonyl bond breaks, the oxygen will carry a negative charge.
- The structure is cyclic, planar, and has 6 pi electrons, which means it is aromatic.
- Aromatic compounds are stable, so the negative charge on oxygen is stabilized.
- **Conclusion**: This will form the strongest hydrogen bond with water.

#### Option C:
- When the carbonyl bond breaks, the oxygen will carry a negative charge.
- The structure forms a 3-membered ring, which introduces angle strain and instability.
- The positive charge is also not stabilized.
- **Conclusion**: This will not form a strong hydrogen bond with water.

#### Option D:
- When the carbonyl bond breaks, the oxygen will carry a negative charge.
- The structure is non-planar and non-aromatic due to sp³ hybridization.
- Non-aromatic compounds are less stable than aromatic ones.
- **Conclusion**: This will not form a strong hydrogen bond with water.

### Step 3: Final Conclusion
After analyzing all options, we find that **Option B** has the most stable negative charge on the carbonyl oxygen, allowing it to form the strongest hydrogen bond with H₂O.

### Answer:
**Option B** is the correct answer; it forms the strongest hydrogen bond with water.

---