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.
Enantiomer vs Diastereomer
The main difference Between Enantiomer and Diastereomer is their properties. Their configuration and structure vary from each other. The previous has similar molecular shapes, physical and chemical properties, whereas the succeeding stereoisomers differ from one another. Enantiomers are related by their reflection operation, conversely, diastereomers are not.
Comparison Table Between Enantiomer and Diastereomer
| 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 the interaction 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 | Always they 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 examples. | Tartaric Acid is one of its examples. |
What is Enantiomer?
The stereoisomers with mirror images of each other are called as Enantiomers; because they are related by the reflection operation. 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, 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 examples.
What is Diastereomer?
Likely, Enantiomers, Diastereomers are also called as 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, 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 examples.
Main Differences Between Enantiomer and Diastereomer
- Enantiomers are speculum portrayals of each other, whereas Diastereomers are non-speculum portraits of each other.
- The first is relevant to the reflection procedure, while the second is not.
- Few of the enantiomers have only one stereocenter. Unlike the enantiomer, any of the diastereomers do not have only one stereocenter.
- All stereoisomers of the former pass an optical activity. Conversely, few of the stereoisomers of the latter does not pass it.
- Enantiomer has similar physical and chemical properties, whereas the diastereomer has different.
- The previous has similar molecular shapes. And the succeeding does not.
- Enantiomers have equally opposite rotational angles. On the other hand, diastereomers do not have equal rotational angles.
- The first stereoisomers are not separable by chromatography or crystalization processes. Contrarily, the second ones can be separated by them.
- The former appears in pairs of molecules while the latter in several separated molecules.
- R and S configurations of the previous are different, and the succeeding has similar.
Conclusion
There are various types of stereoisomers and of them, Enantiomers and Diastereomers are often confused. Both of the stereoisomers are different from one another. They are non-superimposable molecules.
Enantiomers are speculum portraits of each other, whereas Diastereomers are non-speculum portraits of each other. But enantiomers have more stereocenters. But some of them have only one. While diastereomers can never have only one stereocenter. They always have two or more.
References
- https://pubs.acs.org/doi/abs/10.1021/ja00095a053
- https://link.springer.com/article/10.1007%252FBF00798778
- https://www.sciencedirect.com/science/article/pii/S0021967302017685
This Article has been written by: Supriya Kandekar