In which delocalisation of positive charge is possible?

Options

A.
B.
C.
D.

Explanation

To determine in which scenario the delocalization of positive charge is possible, we will analyze each option step by step.

### Step 1: Analyze Option A
- **Structure**: A nitrogen (N) atom with three hydrogen (H) atoms and a positive charge.
- **Delocalization Attempt**: If we try to delocalize the positive charge by turning a bond, we would end up with a structure where nitrogen has 10 electrons.
- **Conclusion**: This is not possible because nitrogen can only accommodate a maximum of 8 electrons in its valence shell. Therefore, positive charge delocalization is not possible in option A.

### Step 2: Analyze Option B
- **Structure**: A nitrogen atom with two hydrogen atoms and a double bond, along with a positive charge.
- **Delocalization Attempt**: Trying to delocalize the positive charge by shifting a bond results in nitrogen again having 10 electrons.
- **Conclusion**: This is also not possible, as nitrogen cannot exceed its octet. Thus, positive charge delocalization is not possible in option B.

### Step 3: Analyze Option C
- **Structure**: A positively charged hydroxyl group (OH2+).
- **Delocalization Attempt**: Attempting to delocalize the positive charge by breaking a bond leads to a situation where the oxygen would have more than 8 electrons.
- **Conclusion**: This is not feasible since oxygen cannot accommodate more than 8 electrons. Hence, positive charge delocalization is not possible in option C.

### Step 4: Analyze Option D
- **Structure**: A structure with multiple double bonds and a positive charge.
- **Delocalization Attempt**: If we attempt to delocalize the positive charge by breaking a bond, we can create a double bond while maintaining the octet rule for the involved atoms.
- **Conclusion**: In this case, the delocalization of positive charge is possible without violating the octet rule. Therefore, option D is the correct answer.

### Final Answer
The delocalization of positive charge is possible in **Option D**.

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