Types of Structural Isomerism

Organic Chemistry is a very important part of Chemistry and one of the important topics in organic chemistry is isomerism in the different compounds. These types of changes in the structure of the compound also lead to changes in the properties of the compounds. The word “ISOMERISM” has two words, that is “iso” which means the “same” whereas the other word is “meros” which means “parts”. Follow up on this article to know more.

Structural Isomerism

Structural Isomerism is a type of isomer that has been arranged in a different order but has the same molecular formula.

All these molecules have a similar kind of molecular formula that have different connections that depend on the order in which they are put. As the number of carbon atoms increases the variety of structural isomers increases. 

This phenomenon where the structure of the isomer changes with the same molecular formula is known as the structural isomers.

There is no reference to the spatial arrangement in the structural isomer. The other name for structural Isomerism is known as constitutional isomerism according to the IUPAC naming. In simpler words, it is the type of isomerism in which the number of atoms of a certain element is fixed but its structure changes to form a new compound with new properties.

Structural Isomerism and its types

The structural isomerism has been divided into more sub-parts which are mentioned below:

• Chain isomerism
• Functional group isomerism
• Metamerism isomerism
• Positional isomerism
• Ring-Chain isomerism
• Tautomerism isomerism
• Chain Isomerism

Chain isomerism is that type of isomerism in which there is a difference in the Chain of the carbon atoms, which is known as the chain isomer. This phenomenon is recognized as chain isomerism. In simple words, the chain isomerism shows the difference in the arrangement of the carbon atoms that the compound found can be branched or a chained compound. A few examples are mentioned below:

For Example, let us take the example of Hexane (C6H14). Hexane can make four more different compounds with the same molecular formula. The other compounds are 2-methyl Pentane, 2,3 dimethyl butane, 3- methyl pentane, and 2,2 – dimethylbutane.

• Functional group isomerism

Functional group isomerism is a type of isomerism in which there is a change in the position of the functional groups and the chemical formula of that compound remains the same. These types of compounds are known as the functional isomers and this phenomenon has been recognized as the functional group isomerism. Some of the examples have been mentioned below.

For Example, Taking the example of Alcohols and Ethers, ethanol has the functional group of alcohol (-OH) whereas the ether that can be formed by the same formula is dimethyl ether(R-OR’). As the molecular formula of the compound remains the same in both cases, that is C2H6O.

• Metamerism Isomerism

Metamerism isomerism is a type of isomerism in which there is a difference in the alkyl group that is attached to the functional groups that are known as metamerism isomers and this phenomenon is recognized as the Metamerism Isomerism.

For Instance, methyl propyl ether and diethyl ether

• Positional Isomerism

The positional isomer is a type of isomer that shows the difference in the functional groups and the bonds in the compound, they are known as the positional isomer and the phenomenon is named positional isomerism. 

For Example, 1-butanol and 2-butanol (the difference in the position of the -OH group)

• Ring-Chain Isomerism

The type of isomers in which one of the isomers has an open chain and the other one has a closed chain or a ring-type structure, this type of isomerism is called Ring chain isomerism.

For Example, Cyclobutene, and Butene

• Tautomerism isomerism

When there is a difference in the position of the atoms of hydrogen atoms or the position of protons and electrons is known as tautomer and this phenomenon is known as tautomerism.  This is also known as Desmotropism, it can only occur when it is in the equilibrium state.

For instance, The tautomerism in acetone (keto-enol)

Conclusion

As mentioned above, isomerism happens when compounds with the same molecular formula form different structures with different chemical and physical properties. There are 2 types of isomerism: the first one is stereoisomerism, and the other is structural isomerism. The above article talks about the various types of structural isomers which are: chain isomerism, functional group isomerism, metamerism isomerism, tautomerism isomerism, Positional isomerism, and ring chain isomerism. The FAQs section attempts to address the most probable queries that might arise and provides additional information which will add a better understanding of the topic.