Question

Which of the given statement(s) about N, O, P and Q with respect to M is (are) correct?

`A.` M and N are non–mirror image stereoisomers
`B.` M and O are identical
`C.` M and P are enantiomers
`D.` M and Q are identical

Answer 1

Get a model kit if you don't have one already, that's really the only way to master stereochemistry.

I'm doing these determinations in my head because I've played with the model kit for countless hours. It's wonderful how practice can enable you to do these things, I urge you to as well.

M and N are just the same sawhorse projection flipped around `180°`. However, when we set them equal, you can see they are diastereomers. This is because the front carbon's stereocenter was altered but the back's wasn't in M.

O is M with its back stereocenter rotated `180°C`, thus they are the same molecule.

P is an enantiomer of M because each carbon's stereocenter is inverted, the front is just rotated `180°`.

Q is a diastereomer of M because only its front carbon's stereocenter is inverted.