Which of the following pair is not pair of resonating structures ?

Options

A.
B. `CH_(2)=CH-overset(Theta)O&overset(Theta)CH_(2)-CH=O`
C. `CH_(2)=CH-O-CH_(3)&Coverset(Theta)H_(2)-CH=overset(o+)O-CH_(3)`
D. `CH_(3)-overset(o+)C=O&CH_(3)-C=overset(o+)O`

Answer

To determine which pair is not a pair of resonating structures, we need to understand the concept of resonance in organic chemistry. Resonating structures are different ways of drawing the same molecule that show the delocalization of electrons. For two structures to be considered resonating structures, they must:

1. Have the same arrangement of atoms (the skeleton structure must be the same).
2. Differ only in the arrangement of electrons (bonds and lone pairs).
3. Be able to interconvert by the movement of electrons.

Now, let's analyze the pairs one by one:

### Step 1: Analyze the first pair of structures
- **Structure A**: Contains conjugated double bonds.
- **Structure B**: The double bonds are not conjugated.

Since the second structure does not maintain the conjugation found in the first structure, these two cannot be considered resonating structures.

### Step 2: Conclusion
After analyzing the first pair, we find that they do not meet the criteria for resonance due to the lack of conjugation in the second structure. Thus, the answer to the question is that the first pair is not a pair of resonating structures.

### Final Answer
The answer is option 1.

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