What are Enantiomers?

Enantiomers are molecules that exist in two forms that are mirror images of one another but cannot be superimposed. Enantiomers are also known as enantiomorphs. Since the object and its mirror image are similar, an object with a plane of symmetry cannot be an enantiomer.


Enantiomers are chemically similar in any other way. The direction in which enantiomers rotate polarised light when dissolved in solution, either Dextro (d or +) or Levo (l or -), is what distinguishes them as optical isomers. When two enantiomers are present in equal proportions, they form a racemic mixture, which does not rotate polarized light because the optical activity of each enantiomer cancels out the optical activity of the other.


As we already discussed enantiomers definition now will study what are enantiomers and enantiomers examples in detail.


Physical Properties of Enantiomorph

  1. Physical properties such as melting point, boiling point, infrared absorptions, and NMR spectra are usually similar between enantiomers.

  2. However, although the enantiomer's melting point and other properties would be identical to those of the other enantiomer, the melting point of a mixture of the two enantiomers varies.

  3. This is due to the fact that intermolecular interactions between opposite enantiomers between R and S enantiomers can vary from those between like enantiomers between two molecules with both R and S stereochemistry.

  4. Chiroptical techniques, the most popular of which is optical rotation, are the only physical techniques that can differentiate between a compound's two enantiomers.

  5. The sign and magnitude of the torsional angles, as well as the bond lengths and angles, determine the chiroptical properties of a molecule, with the sign of the torsional angles being the only distinction between enantiomers.


Enantiomorph Structure 

Consider how chirality is formed when a tetrahedrally coordinated atom is bound to four separate substituents, as shown below.

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  • Stereoisomers, which are non-superimposable mirror copies of one another, were first introduced as enantiomers.

  • Any molecule that cannot be superimposable on its mirror image and hence exists as a pair of enantiomers is said to be chiral. Any molecule that can be superimposable on its mirror image, on the other hand, is achiral.

  • Two enantiomers are possible if a molecule contains a single atom that is tetrahedrally bound to four separate substituents.

  • It is important, however, that the four substituents are distinct from one another because if any two of them are the same, the structure would become superimposable on its mirror image, and therefore achiral. A stereogenic core, or simply a stereocenter, is an atom that is bound to four separate atoms.

  • In contrast to chirality, which is a property of the molecule as a whole that cannot be localised around one atom or a group of atoms, a stereocenter is a property of the molecule as a whole that can be localised around one atom or a group of atoms.

  • The existence of a stereocenter is not needed for chirality in a molecule; rather, it is the most common cause of chirality.


Enantiomers Examples

Dextro lactic acid and laevo lactic acid, whose chemical structures are shown below, are an example of a pair of enantiomers.

Given below Is the Enantiomers Examples:

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  • S- and R-methyl chlorophenoxy propionic acid are the names of these isomers (often abbreviated to MCPP and referred to as mecoprop). This compound is thought to be a combination of S- and R-enantiomers, with the R- enantiomer having herbicidal properties. As a result, this substance is often used as a herbicide.

  • It's worth noting that, unlike cis and trans isomers, almost all pairs of enantiomers share physical properties including solubility and melting point. They are suspected, however, to rotate light in opposite directions (both the enantiomers of a compound must be optically active).


Did You Know?

Chiral recognition is the process of distinguishing between a chiral molecule's two enantiomers. It is difficult to distinguish enantiomers from one another since the physical properties that are commonly used to distinguish molecular species are similar. Physical variations can only be found by encounters with a discriminating secondary species.

  1. Chirality is the structural basis of enantiomerism.

  2. Enantiomers are molecules that exist in two forms that are mirror images of one another but cannot be superimposed.

  3. Enantiomers are chemically similar in any other way. The direction in which enantiomers rotate polarised light when dissolved in solution determines whether they are Dextro (d or +) or Levo (l or -) rotatory, hence the term optical isomers.

  4. Since the optical activity of each enantiomer is cancelled by the other, a racemic mixture is formed when two enantiomers are present in equal proportions and do not rotate polarised light.

FAQs (Frequently Asked Questions)

Question1: What is the Difference Between Enantiomers and Diastereomers?

Ans: Enantiomers are stereoisomers that are non-superimposable on each other and exist as mirror copies of each other. Diastereomers, on the other hand, can be identified as stereoisomers with at least two stereocenters. It's important to keep in mind that these isomers are not mirror images of one another.

Question2: Are Enantiomers Chiral or Achiral?

Ans: For example, two pieces of paper are achiral. Chiral molecules, on the other hand, are non-superimposable mirror images of each other, similar to our faces. The mirror image of a Chiral molecule can't be perfectly matched with it, so the mirror images can't be superimposed. Enantiomers are the photos in the mirror.

Question3: Are Enantiomers Optically Active Compounds?

Ans: Yes, all enantiomers have been shown to be optically active. One of the most important properties of enantiomers is their optical activity. This is due to the fact that enantiomers are isomers that are non-superimposable mirror images of each other and hence rotate light in opposite directions.