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
Physical properties such as melting point, boiling point, infrared absorptions, and NMR spectra are usually similar between enantiomers.
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.
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.
Chiroptical techniques, the most popular of which is optical rotation, are the only physical techniques that can differentiate between a compound's two enantiomers.
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.
Chirality is the structural basis of enantiomerism.
Enantiomers are molecules that exist in two forms that are mirror images of one another but cannot be superimposed.
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.
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 on Enantiomorph
1. What is an enantiomorph in Chemistry?
An enantiomorph, more commonly known as an enantiomer in modern chemistry, is one of a pair of stereoisomers that are non-superimposable mirror images of each other. A simple analogy is your left and right hands; they are mirror images but cannot be perfectly overlapped, no matter how you turn them. This structural property is a key concept in stereochemistry.
2. What is the difference between the terms 'enantiomer' and 'enantiomorph'?
In the context of organic chemistry, the terms enantiomer and enantiomorph are often used interchangeably to describe molecules that are non-superimposable mirror images. However, 'enantiomer' is the more precise and widely used term for molecules. The term 'enantiomorph' is also used in crystallography to describe the external forms of crystals that are mirror images of each other.
3. What is the relationship between chirality and enantiomers?
Chirality is the geometric property of a molecule that is responsible for the existence of enantiomers. A molecule is considered chiral if it is non-superimposable on its mirror image. Enantiomers are the actual pair of molecules that represent these mirror images. Therefore, a chiral molecule will always have a corresponding enantiomer.
4. How are enantiomers different from diastereomers?
Both enantiomers and diastereomers are types of stereoisomers, but they are defined by a key difference in their relationship:
- Enantiomers are stereoisomers that are non-superimposable mirror images of each other.
- Diastereomers are stereoisomers that are not mirror images of each other. This situation arises in molecules that have two or more chiral centers.
5. Why are most physical properties of enantiomers, like boiling point, identical?
Enantiomers share the same molecular formula and atomic connectivity. This means their bond lengths, bond angles, and overall molecular structure result in identical scalar physical properties. These include:
- Melting point
- Boiling point
- Density
- Solubility in achiral (non-chiral) solvents
6. How do enantiomers interact with plane-polarised light?
Enantiomers are described as being optically active because they rotate the plane of polarised light. For any pair of enantiomers:
- One isomer will rotate the light in a clockwise direction. This is the dextrorotatory or (+) isomer.
- The other isomer will rotate the light by the exact same degree but in an anti-clockwise direction. This is the laevorotatory or (-) isomer.
7. What is a racemic mixture, and is it optically active?
A racemic mixture, or racemate, is an equimolar (50:50) mixture of a pair of enantiomers. A racemic mixture is always optically inactive. This is because the equal and opposite optical rotations of the two enantiomers cancel each other out, a phenomenon known as external compensation. The net rotation of plane-polarised light is zero.
8. Why is understanding enantiomers crucial in the field of medicine?
Understanding enantiomers is critical in pharmacology because the human body is a chiral environment. Enzymes and cellular receptors are themselves chiral and can interact differently with each enantiomer of a drug. This can lead to one enantiomer being a highly effective therapeutic agent while its mirror image is biologically inactive or, in some cases, toxic. For example, the R-enantiomer of Thalidomide was a sedative, while the S-enantiomer was teratogenic, causing severe birth defects. This makes the separation and use of single-enantiomer drugs essential for safety and efficacy.
