How do you draw a diastereomer?

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Answer 1 · 2016-09-01T01:15:28

You change the configuration of one of the chiral centres.

Diastereomers are stereoisomers that are not superimposable and are not mirror images of each other.

A compound must have at least two chiral centres to have diastereomers.

Let's look at a Compound $"A"$ with two chiral centres.

$"C2"$ and $"C3"$ are chiral centres.

If we change the configuration at $"C2"$ , we get Compound $"B"$ .

This is not a mirror image of $"A"$ , nor is it superimposable with $"A"$ . It is a diastereomer of $"A"$ .

Now, let's change the configuration of just $"C3"$ to get Compound $"C"$ .

This is also a diastereomer of $"A"$ .

BUT, if we change the configuration of both carbon atoms, we get Compound $"D"$ .

This is nonsuperimposable on $"A"$ .

However, it is a mirror image of $"A"$ , because both $"OH"$ groups are on dashes instead of on wedges.

$"A"$ and $"D"$ are enantiomers.