Answer to Question #170514 in Organic Chemistry for sambit

Question

Topocity

Answer 1

Topicity:

In stereochemistry, topicity is the stereochemical relationship between substituents and the structure to which they are attached. Depending on the relationship, such groups can be heterotopic, homotopic,  enantiotopic, or diastereotopic.

1.Homotopic:

Homotopic groups in a chemical compound are equivalent groups. Two groups A and B are homotopic if the molecule remains the same (including stereochemically) when the groups are interchanged with some other atom (such as bromine) while the remaining parts of the molecule stay fixed. Homotopic atoms are always identical, in any environment.

2.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. The two possible compounds resulting from that replacement would be enantiomers.

3.Diastereotopic:

The stereochemical term diastereotopic refers to the relationship between two groups in a molecule which, if replaced, would generate compounds that are diastereomers. Diastereotopic groups are often, but not always, identical groups attached to the same atom in a molecule containing at least one chiral center.

4.Heterotopic:

Heterotopic groups are those that when substituted are structurally different. They are neither diastereotopic nor enantiotopic nor homotopic.