Let's analyze each compound for aromaticity: **Aromaticity Criteria (Hückel's Rule):** 1. The molecule must be cyclic. 2. The molecule must be planar. 3. Every atom in the ring must have a p-orbital (conjugated π system). 4. The ring must have (4n + 2) π electrons, where n is an integer (Hückel's rule). Let's check each option: --- ### 1. Compound 1 - 5-membered ring, with a positive charge, and a methoxy group. - The positive charge on the ring means one less electron for aromaticity. - The π electrons from the two double bonds = 4 π electrons. - Does **not** satisfy Hückel's rule (needs 6 π electrons for aromaticity). --- ### 2. Compound 2 - 6-membered ring, with a nitrogen and an oxygen. - The ring has 2 double bonds (4 π electrons) + lone pair from N (could participate). - However, the oxygen is attached as a nitro group (not contributing to aromaticity). - Not fully conjugated; **not aromatic**. --- ### 3. Compound 3 - Purine-like structure (contains a six-membered ring fused to a five-membered ring). - The six-membered ring is fully conjugated, and the lone pairs on the nitrogens can participate. - The π electron count for the six-membered ring is 6 (aromatic), and the five-membered ring also supports aromaticity. - **This compound is aromatic.** --- ### 4. Compound 4 - 5-membered ring with a nitrogen (positive charge) and two ethyl groups. - The positive charge on nitrogen means it is sp2 hybridized, and all atoms can participate in delocalization. - 2 double bonds (4 π electrons). - Does **not** satisfy Hückel's rule (needs 6 π electrons for aromaticity). --- ## **Final Answer:** **Compound 3 is aromatic.**