See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Analysis of Aromatic Compounds **Step 1: Recall Hückel's Rule** Aromatic compounds must satisfy: - Cyclic structure - Planar geometry - Continuous $p$-orbital overlap - $(4n+2)$ π electrons, where $n = 0, 1, 2, ...$ **Step 2: Evaluate Each Option** **(A) Pyrimidine** ($C_4H_4N_2$) - 6-membered ring with 2 nitrogen atoms - π electrons: $4 + 2 = 6$ (follows $4n+2$ rule with $n=1$) ✓ - Planar and cyclic ✓ - Aromatic ✓ **(B) Pyrylium cation** ($C_5H_5O^+$) - Positive charge on oxygen - π electrons: 6 (follows rule) - However, contains a positively charged oxygen — lacks full aromaticity in typical sense; less stable **(C) Boron-containing compound** - Boron has only 3 valence electrons - Incomplete electron sextet; non-aromatic **(D) Anion (benzene with negative charge)** - Extra electron makes it antiaromatic - π electrons: 8 (follows $4n$ rule with $n=2$) — destabilizing ✗ **Answer: (A)** — Pyrimidine is a stable aromatic heterocycle that perfectly satisfies Hückel's criteria with 6 π electrons in a planar conjugated ring system.