Brief Notes on Origin of Optical Isomers

What are isomers?

Molecules with the same molecular formula but different atomic arrangements are known as isomers.

Isomerism can be divided into two types.

• Isomerism in structure
• Stereoisomerism

What are Optical isomers? 

Optical isomers are two compounds with the same number and kinds of atoms, bonds (i.e., atom connectivity), and different spatial arrangements of the atoms but non-superimposable mirror images. Chirality refers to molecules or ions that exist as optical isomers.

Origin of Optical Isomers

The nature of optical isomerism is defined, as well as the problem of optical asymmetry’s origin in relation to the origin of life. Particle physics advances are discussed, including the discovery of parity non-conservation in weak interactions and, more recently, neutral currents. Their significance stems from the fact that there are a variety of mechanisms by which the fundamental asymmetry of matter could be reflected in a preference for one enantiomer over the other and that optical isomers do not have identical energy contents, contrary to long-held beliefs; however, the difference is estimated to be very small. Theories about the origin of optical asymmetry are categorised in a two-dimensional matrix (origin by chance or due to pre-existing order; experimentally susceptible or not susceptible).

Organic molecules with the same chemical formula but different atom arrangements are known as isomers. Optical isomers, on the other hand, are isomers that are mirror images of one another. They come in pairs, just like your hands, and are not interchangeable. Enantiomers are the different types of optical isomers, and asymmetry refers to the central carbon atom that holds each molecule together. Furthermore, just as your hand has four different fingers, this type of molecule must have four different groups in addition to the central carbon atom, and they must be distinct from one another.

What is optical isomerism?

Optical isomerism is a type of Stereoisomerism. Isomers are compounds that have the same molecular formula but differ in their atom bonding arrangements. Stereoisomers, on the other hand, have the same molecular formula and atom bonding arrangement.

They do, however, have a variety of spatial (three-dimensional) atoms. It eliminates all different configurations that result from the molecule spinning in its entirety or revolving around the unique bonds.

Enantiomers are optical isomers of the same compound that have similar physical properties but differ only in the properties of plane-polarised light rotation. One isomer, known as dextrorotatory, rotates plane-polarised light to the right, while its optical isomer, known as laevorotatory, rotates the same plane-polarised light to the left.

Geometrical isomers are stereoisomers with the same substituents attached to a carbon-carbon double bond in different ways. This isomer forms when the double bond between carbon atoms prevents the isomer from rotating around the double bond’s axis, resulting in fixed positions for the isomer.

Because geometrical isomers come in pairs, they are also known as cis-trans isomers. Cis-isomer and trans-isomer are two types of isomers.

The main distinction between optical and geometrical isomers is that optical isomers are mirror images of each other, whereas geometrical isomers are pairs of compounds with the same substituents attached to a carbon-carbon double bond in different ways.

Optical isomers in coordination compounds

More on Coordination Number and Geometric Isomerism:

This type of isomerism can be found in heteroleptic complexes. The multiple geometric arrangements of ligands around the central metal atom are the main reason for this.

This isomerism is most common in coordination compounds with coordination numbers of 4 and 6.

Coordination compounds with coordination number 4 have a [MX2L2] type formula, where X and L are unidentate ligands. In a cis isomer, the two ligands X could be next to each other, while in a trans isomer, they could be opposite to each other.

Three isomers are visible in square planar complexes with the MABXL type formula: two cis and one trans.

These isomers are not visible in a tetrahedral geometry. Octahedral complexes, on the other hand, do show cis and trans isomerism. The X ligands can be arranged in cis or trans to each other in complexes with the formula [MX2L4].

When bidentate ligands L–L [e.g., NH2 CH2 CH2 NH2 (en)] are present in complexes with the [MX2(L–L)2] type formula, we see this type of isomerism as well.

Another type of geometrical isomerism that we see in octahedral coordination entities with the [Ma3b3] type formula is found in octahedral coordination entities with the [Ma3b3] type formula. [Co(NH3)3(NO2)3] is an example.

Example of optical isomerism

Carbon has hydrogen, chlorine, fluorine, and a methyl group attached to it, making it a chiral centre. It, therefore, exists in these two enantiomeric forms. The two molecules cannot be superimposed on one another.

Conclusion

Understanding isomerism has aided in the development of both new and existing drug alternatives that are safer and more effective. Many already-existing drugs have gone through chiral switching, in which the racemic mixture has been replaced by one of its isomers.