Which of the following compounds is a meso compound?

• A. 2-butanol ($\mathrm{CH}3-\mathrm{CH}\left(\mathrm{OH}\right)-\mathrm{CH}2-\mathrm{CH}3$)
• B. Tartaric acid ($\mathrm{HOOC}-\mathrm{CH}\left(\mathrm{OH}\right)-\mathrm{CH}\left(\mathrm{OH}\right)-\mathrm{COOH}$)
• C. 2,3-dibromobutane ($\mathrm{CH}3-\mathrm{CHBr}-\mathrm{CHBr}-\mathrm{CH}3$)
• D. $2_{-}$Butanediol (${\mathrm{HOCH}}_2\mathrm{CH}\left(\mathrm{OH}\right)\mathrm{CH}2\mathrm{OH}$)

Answer: (B)

Verified step by step guidance

1. Understand that a meso compound is an achiral molecule that contains multiple stereocenters but has an internal plane of symmetry, making it optically inactive despite having chiral centers.
2. Identify the stereocenters in each compound by locating carbon atoms bonded to four different groups.
3. Examine the symmetry of each molecule: check if the molecule can be divided into two halves that are mirror images of each other, indicating an internal plane of symmetry.
4. For 2-butanol, note it has only one stereocenter, so it cannot be meso because meso compounds require at least two stereocenters.
5. For tartaric acid and 2,3-dibromobutane, analyze the relative configurations of the stereocenters and look for symmetry; tartaric acid has two stereocenters and an internal plane of symmetry, making it a meso compound.