Which of the following structures are resonance structures ?

Options

A.
B.
C.
D. `CH_(3)-CH=CH-CH_(3)&CH_(3)-CH_(2)-CH=CH_(2)`

Answer

To determine which of the given structures are resonance structures, we need to follow these steps:

### Step 1: Understand Resonance Structures
Resonance structures are different ways of drawing the same molecule that show the delocalization of electrons. They must have the same arrangement of atoms but differ in the placement of electrons (bonds and lone pairs).

### Step 2: Analyze Each Option
- **Option 1**: Check if the arrangement of atoms has changed. If it has, it cannot be a resonance structure.
- **Option 2**: Look for a structure where only the electrons are rearranged, not the atoms. If the atoms remain in the same position and only the electrons shift, it is a resonance structure.
- **Option 3**: Determine if the structures are tautomers. Tautomers are structural isomers that can interconvert, typically involving the relocation of a hydrogen atom and a double bond. If they are tautomers, they are not resonance structures.
- **Option 4**: Check if the structures are completely different molecules. If they are not isomers, they cannot be resonance structures.

### Step 3: Conclusion
After analyzing the options:
- **Option 1**: Not a resonance structure (atoms rearranged).
- **Option 2**: Resonance structure (only electrons rearranged).
- **Option 3**: Not a resonance structure (they are tautomers).
- **Option 4**: Not a resonance structure (not isomers).

### Final Answer
The correct answer is **Option 2** as it represents resonance structures.

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