Difference Between Enantiomer and Diastereomer

In chemistry, Isomerism is the existence or possibility of isomers. Molecules or poly-atomic particles in the equivalent molecular formulation are Isomers.

They have a similar number of atoms of every component except with varying combinations in atomic range. Out of its different types, stereoisomers have the same one apart from rotations and translations. 

Stereoisomers are further divided into the following types: Enantiomers, Diastereomers, Conformers, Anomers, and Atropisomers. The first two types are optical isomers.

Their molecules are non-superimposable. They both even have molecular and structural formulae. Yet, they have many differences.

Key Takeaways

1. Enantiomers are non-superimposable mirror images of each other, while diastereomers are stereoisomers that are not mirror images of each other.
2. Enantiomers have identical physical and chemical properties except for the direction in which they rotate plane-polarized light, while diastereomers have different physical and chemical properties.
3. Enantiomers have opposite configurations at all chiral centers, while diastereomers have opposite configurations at some, but not all, chiral centers.

Enantiomer vs Diastereomer 

Enantiomers are a type of stereoisomer that are non-superimposable mirror images of each other. They have identical physical and chemical properties.  Diastereomers are stereoisomers that are not mirror images of each other. They have different physical and chemical properties, such as melting point and boiling point. 

Comparison Table 

Parameters of Comparison	Enantiomer	Diastereomer
Meaning	Stereoisomers that are mirror images of each other are known as Enantiomers.	Stereoisomers that are non-mirror images of each other are known as Diastereomers.
Reflection Operation	Enantiomers are related to their reflection operation.	Diastereomers are not related to their reflection operation.
Optical Activity	Here, all stereoisomers pass an optical activity.	Here, not all of the stereoisomers pass an optical activity.
Properties	All enantiomers have similar physical and chemical properties except for interacting with eight and chiral compounds.	All diastereomers have different physical and chemical properties.
Rotation Angle	These stereoisomers have equally opposite rotational angles.	These stereoisomers do not have equal rotational angles.
Stereocenter	Few of the enantiomers have only one stereocenter.	No diastereomers have only one stereocenter.
Molecular Shapes	It has similar molecular shapes.	It does not have similar molecular shapes.
Separation	They cannot be separable by chromatography or crystalization processes.	They can be separable by chromatography or distillation processes.
R and S Configurations	They always have different R and S configurations.	Commonly they have the same R and S configurations.
Appearance	It appears in a pair of molecules.	It appears in several separated molecules.
Examples	Amino Acid is one of its example.	Tartaric Acid is one of its example.

What is Enantiomer?

The stereoisomers with mirror images of each other are called Enantiomers; because the reflection operation relates them.

Also, they are recognizable as optical isomers. Few of the enantiomers have only one stereocenter, while others can have more than that.

Here, all stereoisomers pass an optical activity. And all of the enantiomers have similar physical and chemical properties except the interaction with eight and chiral compounds. They always have different R and S configurations.

These stereoisomers have equally opposite rotational angles. They appear in pairs of molecules and have similar molecular shapes. And cannot be separated by chromatography or crystalization processes. Amino Acid is one of its example. 

What is Diastereomer? 

Likely,  Enantiomers, Diastereomers are also called optical isomers. But they differ through their reflection operation. They are not related.

Stereoisomers with non-mirror images of each other are known as Diastereomers. Commonly they have the same R and S configurations. But all of the diastereomers have different physical and chemical properties. 

Here, not all of the stereoisomers pass an optical activity. No diastereomers have only one stereocenter. Always, all of the stereoisomers have two or more stereocenters.

They can be separable by chromatography or distillation processes. These stereoisomers do not have equal rotational angles. 

They do not have similar molecular shapes. Even appear in several separated molecules. The stereoisomers of diastereomers include Non-enantiomeric optical isomers, Cis-trans, Meso compounds, and E-Z isomerism. Tartaric Acid is one of its example.

Main Differences Between Enantiomer and Diastereomer

1. Enantiomers are speculum portrayals of each other, whereas Diastereomers are non-speculum portraits of each other.
2. The first is relevant to the reflection procedure, while the second is not.
3. Few of the enantiomers have only one stereocenter. Unlike the enantiomer, any of the diastereomers not have only one stereocenter.
4. All stereoisomers of the former pass an optical activity. Conversely, few of the stereoisomers of the latter do not pass it.
5. Enantiomer has similar physical and chemical properties, whereas diastereomer has different ones.
6. The previous has similar molecular shapes. And the succeeding does not.
7. Enantiomers have equally opposite rotational angles. On the other hand, diastereomers do not have equal rotational angles.
8. The first stereoisomers are not separable by chromatography or crystalization processes. Contrarily, they can separate the second ones.
9. The former appears in pairs of molecules, while the latter appears in several separated molecules.
10. R and S configurations of the previous are different, and the succeeding has similar.

References

1. https://pubs.acs.org/doi/abs/10.1021/ja00095a053  
2. https://www.sciencedirect.com/science/article/pii/S0021967302017685 

This article has been written by: Supriya Kandekar