Difference Between Enantiomers and Diastereomers

Introduction

Enantiomers as well as diastereomers are further classifications of isomers. Isomers are substances which have the same chemical formula but a distinct atom configuration. They are categorised into 2 categories: structural isomers and stereoisomers. The former has the same chemical formula but distinct atom connections. While the latter has molecules that differ in how their structures are arranged spatially. And they are further classified as enantiomers as well as diastereomers. They both are distinguished by the fact that enantiomers are found as mirror images whereas diastereomers are not. For a substance to have stereoisomers, it must be chiral. To be chiral, molecules must have 4 distinct groups linked to a central 𝐶-atom. These groupings must be chemically distinct. The 𝐶-atom in these compounds is known as a chiral carbon or chiral centre. Some complexes may have many chiral centres.

What are Enantiomers ?

They are stereoisomers whose components cannot be superimposed on one another. They are only conceivable with chiral compounds. A chiral compound differs from its mirror copy. A chiral molecule has one tetrahedral 𝐶-atom with 4 distinct groups linked to it. This 𝐶-atom is referred to as a stereocenter. Chiral compounds produce mirror images that cannot be superimposed. As a result, the component and its mirror copy are enantiomers of one another. The following is an example of an enantiomer-forming chemical.

Enantiomers are often named using the R as well as the S method. They do not have variable boiling temperatures, melting points, solubilities, infrared spectra, or other properties. Since intermolecular interactions are similar in both isomers, all of these chemical or even physical characteristics of enantiomers are similar. They are solely distinguished by their varied responses to plane-polarized light. They spin the plane of plane-polarized light in opposing directions. They do, however, spin the light in equal proportions. Enantiomers are optically active due to their influence on polarised light. A racemic mixture is an equimolar combination of 2 enantiomers. A racemic combination exhibits no rotation of polarised light and is hence optically inert.

Example

D-Amino Acid and L-Amino Acid

D-alanine and L-alanine

What are Diastereomers ?

Diastereomers are stereoisomers that do not have mirror reflections of each other. Cis as well as trans isomers e.g., diastereomers. Atoms are connected in the same way here.

Both compounds feature a carbon-carbon double bond (𝐶 = 𝐶). A methyl group and a 𝐻-atom are linked to each carbon (𝐶). The sole difference between cis versus trans molecules is how the atoms are organised in space. Both hydrogens are all on the same end of the carbon double bond (𝐶 = 𝐶) in the cis isomer. The trans isomer, on the other hand, has hydrogen atoms on both sides of the carbon double bond. Furthermore, the 2 structures are not mirrored reflections of one another. As a result, they are diastereomers. However, cis including trans molecules may not be the only types of molecules.

Example

D-Tartaric Acid and meso Tartaric Acid

Ribitol and Xylitol

Types of isomers

Isomers are classified into two types: structural isomers as well as stereoisomers.

• Stereoisomers are isomers that have an identical bond structure but differ in the geometrical location of the atoms and functional groups.

• Structural isomers are compounds that have the same chemical formula but distinct structures, i.e., various atom configurations inside the molecule. The chart below depicts their categorization.

Difference Between Enantiomers and Diastereomers

Enantiomers	Diastereomers
They are chemical substances in which the mirror images are not superimposed.	They are chemical compounds in which the components are not stacked thus nonmirror images are created.
The polarised light they emit in a specific direction distinguishes enantiomers.	Non-mirror images, as well as nonidentical stereoisomers, distinguish diastereomersim.
These are mirror reflections of 1 another.	These are non-mirrored mirror reflections of 1 another.
Except for interaction with chiral substances, all enantiomers have the same chemical as well as physical characteristics.	Each diastereomer has a unique set of physical as well as chemical properties.
There are 1 or 2 stereocenters in enantiomers.	They have at least 2 stereocenters.
Each enantiomer has optical activity.	They have no optical activity.
Enantiomers have equal but opposing rotational angles.	These, unlike enantiomers, have an identical angle of rotation.
They have identical molecular structures.	They have distinct molecular shapes.
They are compounds that exist in paired form.	The molecules in diastereomers exist independently.
They include many R as well as S configurations.	In diastereomers, the R, S arrangement is the same. As a result, this layout may be found in at least 1 stereocenter
Their molecules cannot be separated by crystallisation or chromatography.	Chromatography plus fractional distillation are used to separate compounds in diastereomers.

Conclusion

We may infer from this article that isomers are substances with diverse chemical as well as physical characteristics. The 2 isomers chemical structures differ due to the spatial arrangement of atoms or groups in their compounds. They are classified into 2 groups: structural isomers plus stereoisomers. Because of the existence of chiral centres, stereoisomers are optically active. Stereoisomers are further classified into 2 types: enantiomers as well as diastereomers. The major distinction between enantiomers versus diastereomers is that enantiomers are found as mirror images, but diastereomers are not.

FAQs

1. Show some examples of isomerism?

Following are examples of different Isomerism

• Chain isomerism: 1-bromobutane and 1-bromo −2–methylpropane

• Position isomerism: But 1-ene and But 2-ene

• Functional Isomerism: Methoxy ethane with ethanol

• Metamerism: 1-methoxypropane, 1-methoxypropane, and ethoxyethane

• Rings isomerization: Cyclopropane and propane

• Tautomerism: The hydrocyanic acid

• Geometrical isomerism: cis-but2-ene and trans-but-e-ene

• Optical isomerism: d-lactic acid and I-lactic acid exhibit.

2. What is the connection between mirror images and objects?

Mirror images of symmetric objects can be placed on top of them. It is the same thing. Asymmetric things as well as their mirror equivalents cannot be superimposed. They are 2 separate entities. When it comes to molecules, chiral substances including their mirror counterparts are distinct. Enantiomers are chiral compounds plus their mirror images.

3. What exactly is polarisation? Mention the Fajan’s Rule as well?

Polarization is the deformation of a negatively charged ion's electron cloud by another positively charged ion. As per Fajan’s Rule, the smaller the ion, the greater its propensity to distort the electron cloud of others, while anions with bigger sizes are more prone to distortion.

4. What are the similarities and differences between enantiomers and diastereomers?

• Stereoisomers include both enantiomers as well as diastereomers.

• Both have optically active chiral centres.

• Enantiomers, as well as diastereomers, cannot be superimposed.

5. What exactly do you mean by "superimposable"?

The capacity for 1 item to be put on top of another, generally in such a way that both are visible. Frequently used interchangeably with the larger phrase superimposable (the ability for an object to be placed over another object; without the visibility restriction).