Isomerism- Types and Explanation

What is Isomerism?

Isomerism is the phenomenon where one compound exists in more than one form and all of them have the same chemical formula but with different chemical structures.

Chemical compounds with the same chemical formulas but vary in their properties and arrangement of their atoms inside the molecule are termed isomers. So, compounds that show isomerism are known as isomers.

Isomerism Types

There are two primary types of isomerism, which are further classified into different subtypes. These primary types are structural isomerism and stereoisomerism. 

Structural Isomerism

Structural isomerism is also called constitutional isomerism where the atoms and their functional groups are linked differently. Each such structural isomer has a specific IUPAC name. This is further divided into chain and position isomerism. 

Chain Isomerism

It is the skeletal isomerism where the components are arranged as branched structures. Such isomers only differ in their branching of carbon

Position Isomerism

Here the positions of the functional groups or other atoms are in different positions. They have functional groups attached to different carbon atoms of the same carbon chain.

Functional Isomerism

Otherwise, called the functional group isomerism, it has the compounds with the same chemical formula but differs in their functional groups. 

Metamerism

Here, the isomerism is due to the alkyl chains attached on either side of the functional group. It is a rare occurrence and limited to divalent atoms such as sulphur and oxygen. 

Tautomerism

When two compounds differ only in their position of the nuclear elements such as protons and electrons, they are called tautomers. They are usually interchangeable and are formed through intramolecular proton transfer.

Ring-Chain Isomerism

In ring-chain isomerism one isomer will have an open chain structure while the other one with a ring structure. They also have different pi bonds. 

 Stereoisomerism

Stereoisomerism happens when the compounds have the same chemical formula, but the orientation of their atoms will be different, in the three-dimensional space. The compounds that show this phenomenon are called stereoisomers. 

Stereoisomerism is further classified into two types such as geometric isomerism and optical isomerism,  

Geometric Isomerism

Geometric isomerism is also called cis-trans isomerism. Here the spatial arrangements of the isomers are different in their three-dimensional space. 

Optical Isomerism

Optical isomers are compounds that exhibit Optical isomerism. Here the isomers have similar bonds but in the spatial arrangement, they form mirror images of each other. They are also called enantiomers that differ in their optical activities. The dextro enantiomers will be rotating in the plane of a polarized light towards its right while a laevo enantiomer rotates it to the left side. 

Ionization Isomerism

Such isomers have a similar structure and chemical formulas, but they produce different ions in a solution. Even with the exact composition, the ions that they produce will be different from each other. Such isomers are called ionization isomers. 

Interestingly, an ionization isomer is formed when the compound salts undergo electrolysis. Here, a counter ion itself becomes a potential ligand and can also transform the ligand into a counter ion.