Question

Identify whether each of the structure in the second row is an enantiomer of, is a diastereomer of, or is identical to the structure in the top row.

Short answer

Compound A in the second row is an enantiomer of the top row compound. Because in compound A, there are two chiral carbons (represented by *), A is mirror image of the top compound and both mirror images are non-superimposable on each other.

Step-by-step solution

Step: 1 What are enantiomers:

A compound with one or more chiral center, form mirror image and if both, compound and its mirror image are non-superimposable on each other thus, both are called enantiomers of each other or stereoisomers.

Step:2 Explanation

Compound A, has two chiral centers means there are two carbon present which have four different groups attached to it. Chiral center or carbon is represented by *.

Now, as we form its mirror image we get same compound in top row and both are non-superimposable images. Thus, compound A is enantiomer of compound in top row.

Both are non-superimposable images at 0⁰ rotation or at 180 ⁰rotation.

Step:3 Conclusion

Thus, compound A is an enantiomer of the compound in the top row because compound A is a mirror image of the compound at the top row, and both are non-superimposable images.

Thus, compound D is identical to the compound in the top row because compound D after rotating 60⁰, we get the same compound as a compound in the top row.