Some articles on enantiotopic:

Topicity - Enantiotopic
... The stereochemical term enantiotopic refers to the relationship between two groups in a molecule which, if one or the other were replaced, would generate a chiral compound ... For example, the two hydrogen atoms attached to the second carbon in butane are enantiotopic ... Butane (R)-2-bromobutane (S)-2-bromobutane Enantiotopic groups are identical and indistinguishable except in chiral environments ...