The compound shown is one stereoisomer of 1,2-dichlorocyclohexane drawn with wedges. Consider configuration only. Which of the following statements are correct?

AThe compound shown is $(1 S, 2 S)$
BIts mirror image is $(1 R, 2 R)$ -1,2-dichlorocyclohexane
CExchanging the $Cl$ and $H$ at C1 only gives the $(1 R, 2 S)$ isomer, which is the meso cis compound
DThe compound shown is achiral

Answer: A, B, C

At C1 the priorities are

Cl > C X_{2}

(attached to Cl,C,H)

> C X_{6}

(C,H,H)

> H

, and by symmetry the same pattern holds at C2. The drawing has the two chlorines on opposite faces (trans), and applying the sequence rule gives

(1 S, 2 S)

. Reflection inverts both centres, giving

(1 R, 2 R)

, which is a different molecule, so the compound shown is chiral. Inverting C1 alone gives

(1 R, 2 S)

, where both

Cl

are on the same face; this cis isomer has a mirror plane and is meso.