Which of the following compounds is a meso isomer of $C_4{H}_6{\mathrm{Cl}}_2$ (2,3-dichlorobutane)?

• A. A compound with chlorine atoms on carbons $2$ and $3$, one on a wedge and one on a dash ($2R,3S$)-2,3-dichlorobutane
• B. A compound with both chlorine atoms on carbon $2$ ($2,2$-dichlorobutane)
• C. A compound with chlorine atoms on carbons $2$ and $3$, both on the same side ($2R,3R$)-2,3-dichlorobutane
• D. A compound with chlorine atoms on carbons $1$ and $4$ ($1,4$-dichlorobutane)

Answer: (A)

Verified step by step guidance

1. Identify the structure of 2,3-dichlorobutane, which has chlorine atoms attached to the second and third carbons of a four-carbon butane chain.
2. Determine the stereochemistry at carbons 2 and 3 by assigning R/S configurations based on the Cahn-Ingold-Prelog priority rules, considering the substituents attached to these carbons.
3. Understand that a meso compound is achiral despite having stereocenters, due to an internal plane of symmetry that makes the molecule superimposable on its mirror image.
4. Check which stereoisomer has opposite configurations at carbons 2 and 3 (i.e., one is R and the other is S) and has a plane of symmetry, indicating it is a meso isomer.
5. Exclude compounds with chlorines on the same carbon or on carbons 1 and 4, as these do not have the correct stereochemical arrangement or symmetry to be meso isomers.