See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

A meso compound is one that has chiral centers but is achiral overall due to an internal plane of symmetry, making it non-resolvable into enantiomers. Concept: A meso compound contains stereocenters yet is superimposable on its mirror image because of an internal plane (or point) of symmetry. Analysis of each option: (a) The cyclohexane derivative shown has two adjacent carbon stereocenters each bearing a Br and H substituent. In the depicted configuration (both Br groups on the same face, i.e., cis relationship), the molecule possesses an internal mirror plane bisecting the ring between the two stereocenters. The cis-1,2-dibromocyclohexane is a meso compound because the two halves of the molecule are mirror images of each other, making the overall molecule achiral and non-resolvable. (b) The cyclopentane diol shown has a methyl group and two OH groups at specific stereocenters. With Me on a wedge at one carbon and the OH groups arranged such that an internal plane of symmetry exists within the ring system, this compound qualifies as a meso compound. (c) The cyclohexane with multiple Br substituents arranged symmetrically about the ring also has an internal plane of symmetry relating the two halves of the molecule, making it a meso compound as well. Since all three structures (a), (b), and (c) represent meso (non-resolvable) compounds due to internal planes of symmetry despite having stereocenters, option (d) 'All of these' is correct. Why other options fail: Options (a), (b), and (c) alone are each individually correct, but since the question asks which compound is a meso compound and all three qualify, the most complete answer is (d). Therefore, the correct answer is D.