The question is to find the TOPICITY relationship between Ha and Hb in the given compound, (trans 1,3 dichlorocyclobutane)
They seem to be in the same chemical environment, so I tried the substitution method, and replaced Ha and Hb with an X* atom in-turn (for convenience, I have used Br as the X* atom ). Then, I used CIP rules to assign priority, and got RR and SS configuration respectively. (See img below) I concluded them to be enantiotopic.
However, I am still confused because I cannot imagine any plane which would be used to show the mirror image relationship between the two.
Is my answer and reasoning correct?
If so, kindly demonstrate the mirror plane which makes the two compounds enantiomers.
If not, please explain.
Nb: I couldn't find an axis of symmetry that makes Ha and Hb equivalent. That led me to the conclusion that thay are not Homotopic.