Which of the following is not a resonance form of para-amino-benzaldehyde ?

Options

A.
B.
C.
D.

Answer

To determine which of the given options is not a resonance form of para-amino-benzaldehyde, we first need to understand the structure of para-amino-benzaldehyde and its possible resonance forms.

### Step-by-Step Solution:

1. **Identify the Structure of Para-Aminobenzaldehyde**:
- Para-amino-benzaldehyde consists of a benzene ring with an amino group (-NH2) at the para position relative to the aldehyde group (-CHO).
- The structure can be represented as:
```
NH2
|
C6H4 - CHO
```

2. **Draw the Resonance Structures**:
- The resonance structures can be drawn by shifting the lone pair of electrons and pi bonds.
- One possible resonance structure involves the lone pair on the nitrogen atom forming a double bond with the carbon atom of the benzene ring, while the double bond between the carbon and oxygen in the aldehyde shifts to form a negative charge on the oxygen:
```
+NH2
||
C6H4 - C^(-) - OH
```
- Another resonance structure can be formed by shifting the double bond from the carbonyl (C=O) to the nitrogen, resulting in:
```
NH2^+
||
C6H4 - C - O^(-)
```

3. **Analyze the Given Options**:
- We need to evaluate each option to see if it can be a valid resonance form.
- If any structure shows a carbon atom with a valency greater than 4 (i.e., pentavalent), it cannot be a valid resonance structure.

4. **Evaluate Each Option**:
- **Option 1**: Valid resonance structure (as derived).
- **Option 2**: This structure shows a carbon atom with five bonds (pentavalent), which is not possible. Therefore, this is not a valid resonance structure.
- **Option 3**: Valid resonance structure (similar to the ones derived).
- **Option 4**: Valid resonance structure (as derived).

5. **Conclusion**:
- The option that is not a resonance form of para-amino-benzaldehyde is **Option 2**, as it depicts a carbon atom with a valency of 5, which is not feasible.

### Final Answer:
**Option 2 is not a resonance form of para-amino-benzaldehyde.**