Question

Among the following, the number of aromatic compound(s) is ............. 

Hint:

Aromatic heterocycles often follow a 6π electron system, similar to benzene.

Answer 1

Correct Answer: 4

Step 1: Apply Huckel’s rule (4n+2 π electrons).
A compound is aromatic if it is:
• cyclic
• planar
• fully conjugated
• has (4n + 2) π electrons
Step 2: Examine each given compound.
1. **Phthalic anhydride derivative** → conjugation is broken in carbonyl groups → non-aromatic.
2. **Imide ring (cyclic imide)** → not fully conjugated → non-aromatic.
3. **Borole derivative** → 4π electrons → antiaromatic → not aromatic.
4. **1,3,4-oxadiazole derivative** → 6π system → aromatic → yes.
5. **Furan derivative** → 6π electrons → aromatic → yes.
Therefore, only three are aromatic:
• the 1,3,4-oxadiazole derivative
• the N-methyl imidazole-like structure
• the furan derivative
Step 3: Conclusion.
Thus, the number of aromatic compounds is 3.