Question: is 2r 3s dibromobutane chiral?
Answer: A meso form is a stereoisomer of a compound with two or more chiral centers that is superimposable on its own mirror image. You may wonder why we can refer to this single meso isomer as either (2R,3S) or (2S,3R). ... Because it has a meso form, 2,3-dibromobutane has only 3 unique stereoisomers.