Which of the following compounds can exist as a meso isomer?

• A. $2,3$-dibromobutane
• B. $2$-pentanol
• C. $2$-butanediol
• D. $2$-chloropropane

Answer: (A)

Verified step by step guidance

1. Step 1: Understand what a meso compound is. 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. Step 2: Identify the stereocenters in each compound. Look for carbon atoms bonded to four different groups, which are potential chiral centers.
3. Step 3: For each compound, determine if it has more than one stereocenter. Meso compounds require at least two stereocenters to have the possibility of internal symmetry.
4. Step 4: Analyze the symmetry of the molecule. Check if the molecule can be divided into two halves that are mirror images of each other, which would indicate the presence of an internal plane of symmetry.
5. Step 5: Conclude which compound(s) can exist as meso isomers by confirming the presence of multiple stereocenters and internal symmetry, such as in 2,3-dibromobutane, which has two stereocenters and a plane of symmetry.