Among the given sets, which represents the resonating structures ?

Options

A. `H-C-=overset(+)N-overset(..)underset(..)O:^(-) and H - overset(..)underset(..)O-C-=N:`
B. `H-underset(..)overset(+)O=Coverset(..)N:^(-) and H-overset(..)underset(..)O-C-=N:`
C. `H-C-=overset(+)N-overset(..-)underset(..)O: and H - overset( :O: )overset(||)C-overset(..)N:`
D. ` H-overset(..)underset(..)O-C-=N:^(-)and H-overset(..)N=C=overset(..)O:`

Explanation

To determine which of the given sets represents resonating structures, we need to understand the concept of resonance in organic chemistry. Resonance occurs when there are multiple valid Lewis structures for a molecule that differ only in the arrangement of electrons, particularly pi electrons or lone pairs, while the positions of the atoms remain unchanged.

### Step-by-Step Solution:

1. **Identify Resonating Structures**:
- Resonating structures must have the same arrangement of atoms but differ in the placement of electrons (specifically pi electrons or lone pairs).

2. **Examine Each Set**:
- **Set 1**: Check if the structures differ only in electron placement.
- In this set, the structures have different bonding arrangements (O-H vs. C-H), indicating they are different compounds, not resonating structures.
- **Set 2**: Analyze the structures for electron movement.
- Here, we have H-O⁺ and C≡N⁻. The negative charge can move to form a double bond between C and O, while the triple bond remains intact. This indicates that these structures can interconvert by the movement of electrons, thus they are resonating structures.
- **Set 3**: Check for validity of resonance.
- The structures in this set show a negative charge moving, but they result in a different compound due to the change in bonding (C-O bond appears in one structure but not in the other). Hence, they are not resonating structures.
- **Set 4**: Analyze the changes in bonds.
- In this case, while there is some movement of electrons, the resulting structure does not maintain the same connectivity of atoms, indicating they are different compounds, not resonating structures.

3. **Conclusion**:
- After examining all sets, only **Set 2** represents valid resonating structures, as they maintain the same arrangement of atoms while differing in electron placement.

### Final Answer:
The correct answer is **Set 2**.

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