See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

Concept: A chiral molecule is one that is non-superimposable on its mirror image. The most common source of chirality is a stereocenter (sp3 carbon bearing four different substituents). Step 1 - Analyze option (a) 3-methyl-3-hexene: The structure is CH3-CH2-C(CH3)=CH-CH2-CH3. C3 is part of a double bond (sp2, trigonal planar) and therefore cannot be a stereocenter. No other sp3 carbon bears four different groups. Not chiral. Step 2 - Analyze option (b) 4-chloro-1-methylcyclohexane: This is a cyclohexane ring with a methyl group at C1 and a chlorine at C4. C1 has: methyl, H, and two ring carbons (C2 and C6). C4 has: Cl, H, and two ring carbons (C3 and C5). In the parent numbering, C3 and C5 are equivalent (symmetric), and C2 and C6 are equivalent (symmetric), making both C1 and C4 not true stereocenters (they each have two identical substituents via the ring). The molecule has a plane of symmetry. Not chiral. Step 3 - Analyze option (c) 2-phenylpentane: The structure is C6H5-CH(CH3)-CH2-CH2-CH3. C2 bears: a phenyl group, a methyl group (CH3), a hydrogen (H), and a propyl chain (CH2CH2CH3). All four substituents are different, making C2 a true stereocenter. This molecule is chiral. Step 4 - Analyze option (d) 1,3-diisopropylbenzene: The benzene ring with two identical isopropyl groups at positions 1 and 3 has a plane of symmetry through the ring. The isopropyl groups themselves are -CH(CH3)2, where the central carbon bears two identical methyl groups, so no stereocenter exists. Not chiral. Conclusion: Only 2-phenylpentane (option c) possesses a true stereocenter with four different substituents and no internal plane of symmetry, making it chiral. Therefore, the correct answer is C.