See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Analysis of Aromatic Compounds **Hückel's Rule for Aromaticity:** A compound is aromatic if it satisfies: - Cyclic structure - Planar geometry - Fully conjugated (continuous p-orbitals) - Contains $(4n+2)$ π-electrons (where $n = 0, 1, 2, ...$) **Evaluating each option:** **(1) Cyclopropene:** - 3-membered ring with 1 double bond = 2 π-electrons - $2 \neq (4n+2)$ for any integer $n$ → **Not aromatic** - High ring strain makes it non-planar **(2) Cyclopentadiene:** - 5-membered ring with 2 double bonds = 4 π-electrons - $4 \neq (4n+2)$ → **Not aromatic** - The CH₂ group (saturated) breaks conjugation **(3) Pyridine:** - 6-membered aromatic heterocycle with N - Contains 3 double bonds + lone pair on N = 6 π-electrons - $6 = 4(1)+2$ ✓ → **Aromatic** (satisfies Hückel's rule) - Planar, conjugated ring system **Conclusion:** Only option (3) pyridine is aromatic. However, if the answer key states **(4) All the above**, it likely contains an error, as compounds (1) and (2) do not meet aromaticity criteria. **The chemically correct answer is (3) Pyridine.**