Difference Between Enantiomers vs Diastereomers

Chemistry is a foundational branch of science, yet it is also one of the hardest subjects to learn. Since it deals with a lot of technical terms, not to mention the complicated rules, it is vital that your knowledge of chemistry has a strong baseline. In this piece, we’ll look at one particular topic in Chemistry that’s particularly tricky: chirality in stereochemistry.

 Chirality refers to a property of matter, for example, a molecule, to be identifiable from its mirror image. For example, human hands are chiral, compounds are chiral, the left hand is a mirror image of the right. To further explain how that works, we’ll look at enantiomers vs diastereomers and then provide a foundational definition for these terminologies, and set out how they compare.

Definition of Enantiomers

Enantiomers are molecules that come in twos. They are described as being chiral and mirror copies of each other, and this is one key difference between enantiomers and diastereomers. They are similar to our hands in that you cannot lay one hand on top of the other and expect them to fit together perfectly.

To use a more technical term, these molecules cannot be superimposed. Consequently, just like how your thumbs are pointing in opposite directions, these molecules have opposite polarities.

For this reason, they can be named with an R- or S- or D- or L- to clearly distinguish them. Note that since organic molecules have a base carbon, this polarity is dependent on the rotation of their chiral center.

With them coming together and being rotationally distinct from each other, this variation in polarity can mean diverse molecular characteristics even with similar centers.

For example, thalidomide used to be known as an effective sedative, and indeed it was, until it was realized that the other part of the pair in the mix leads to birth defects. Since they cannot be separated from one another, the drug distribution was discontinued globally.

Definition of Diastereomers

Diastereomers are similarly considered a stereoisomer because they can come in more than one orientation. Just like enantiomers, this rotational variance can result in varied properties, chemically.

However, the isomers of this kind are not considered mirror copies. Therefore, this means that they cannot be overlapped with one another but can share a common center. Since their stereocenter can be more than one, it can result in numerous varieties. Think of 5 common forks with different lengths of prongs.

Due to this variance, they have inconsistent characteristics, and one fork variant may be more preferred than the other. Some prefixes are used to identify one from another, and these are placed before the compound’s name in place of the usual R- and S- or D- and L-; these prefixes can also include syn and anti and threo and erythro.

Main Differences Between Enantiomers vs Diastereomers

To deepen your awareness of the difference between diastereomers and enantiomers, here’s a tabular rundown of their characteristics:

Basis of Comparison	Enantiomers	Diastereomers
Appearance	Their images are mirroring one another but cannot be overlayed	Their images are not mirroring one another and cannot be overlayed
Direction	Polarizations are opposite to one another.	Polarization can be rotational.
Structural comparison	Molecular structures are similar.	Molecular structures can show various differences.
Properties comparison	Similar in physical-chemical properties but can be varied in optical properties.	Varied in physical-chemical properties.
Occurrence	They come in pairs.	There can be multiple stereoisomers.

Their distinction is quite apparent in that one of them comes in a duo and the other can come with more than one similar member. They show a distinction spatially as well, which makes identifying them less tricky.

Difference Between Enantiomers and Diastereomers: Conclusion

In the case of diastereomers vs enantiomers, it is clear that the latter’s structures are more closely related than those of the former. With this distinction alone, it is quite easy to identify them from one another. One other tip in determining one from another is whether they’re polar opposites or not.

If they are, and there’s only two of them, then you’re looking at the latter. If they aren’t, then you’re looking at the former. Clearly, it is essential that Chemistry students learning grasp this concept fully. This will allow for more accurate chemical compound-naming, and property identification.