Which of the following compounds is a meso compound?

• A. 2,3-Dibromopentane (${\mathrm{CH}}_3-\mathrm{CH}\left(\mathrm{Br}\right)-\mathrm{CH}\left(\mathrm{Br}\right)-\mathrm{CH}-{\mathrm{CH}}_3$)
• B. 2,3-Dibromobutane (the compound ${\mathrm{CH}}_3-\mathrm{CH}\left(\mathrm{Br}\right)-\mathrm{CH}\left(\mathrm{Br}\right)-{\mathrm{CH}}_3$ with (2R,3S) configuration)
• C. 2,3-Dimethylbutane (${\mathrm{CH}}_3-\mathrm{CH}\left({\mathrm{CH}}_3\right)-\mathrm{CH}\left({\mathrm{CH}}_3\right)-{\mathrm{CH}}_3$)
• D. 2,3-Butanediol (${\mathrm{CH}}_2\mathrm{OH}-\mathrm{CH}\left(\mathrm{OH}\right)-\mathrm{CH}\left(\mathrm{OH}\right)-{\mathrm{CH}}_2\mathrm{OH}$)

Answer: (B)

Verified step by step guidance

1. Identify the definition of a meso compound: it is an achiral compound that contains multiple stereocenters and an internal plane of symmetry, making it optically inactive despite having chiral centers.
2. Examine each compound's structure to determine the number of stereocenters and check for symmetry. For example, 2,3-dibromopentane has two stereocenters at carbons 2 and 3, but the molecule lacks symmetry due to the pentane backbone.
3. Focus on 2,3-dibromobutane, which has two stereocenters at carbons 2 and 3. Assign configurations (R or S) to these centers and check if the (2R,3S) or (2S,3R) stereoisomer has an internal plane of symmetry.
4. Confirm that the (2R,3S) stereoisomer of 2,3-dibromobutane is superimposable on its mirror image due to the plane of symmetry, making it a meso compound.
5. Verify that other compounds like 2,3-dimethylbutane and 2,3-butanediol either lack stereocenters or do not have the required symmetry to be meso compounds.