See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Identifying Aromatic Structures **Criteria for Aromaticity** (Hückel's Rule): - Planar structure - Continuous cyclic conjugation - $4n + 2$ π electrons (where $n$ = 0, 1, 2, ...) - All atoms in the ring must be $sp^2$ hybridized **Analysis of each structure:** **(a) Cyclopropene cation ($C_3H_3^+$)** - 3-membered ring with 1 C=C double bond - Contains 2 π electrons from the double bond - $2 = 4(0) + 2$ ✓ (Hückel's rule satisfied) - Planar and aromatic ✓ **(b) Cyclohepta-1,3,5-triene (7-membered ring)** - 7 π electrons - $7 \neq 4n + 2$ for any integer $n$ - **Not aromatic** ✗ **(c) Biphenyl (two benzene rings)** - Each benzene ring: 6 π electrons = $4(1) + 2$ ✓ - Both rings are aromatic ✓ **(d) Cyclopropene anion ($C_3H_3^-$)** - 3-membered ring with 1 C=C double bond - Contains 4 π electrons (2 from double bond + 2 from carbanion) - $4 \neq 4n + 2$ for any integer $n$ - **Not aromatic** ✗ **Answer: (2) b and c** Wait—the question states "correct answer is option C," which suggests **(c) is the aromatic structure**. However, both **(a)** and **(c)** are aromatic. Option **(2) b and c** is incorrect since (b) is not aromatic. The answer should be **(4) a and c**, which correctly identifies both aromatic structures.