Structural isomers are those isomers in which the atoms are completely arranged in a different order with the same molecular formulas.
These are the molecules having the same kind of molecular formula with different connectivities depending upon the order they are put together. The structure of alkane (C4H10) is one of the simple examples representing a structural isomer with different isomers. With the increase in the number of carbon atoms in the alkane molecule, the structural isomers increase.
The isomers differing in the atomic arrangement of the molecules without any kind of reference to the spatial arrangement are known as structural isomers. The phenomenon of these structural isomers is called structural isomerism.
Structural isomerism is also called constitutional isomerism, as per the IUPAC. It is a kind of isomerism where the molecules have the same molecular formula with different orders and bondings, as opposed to that of stereoisomerism.
Read More: Isomers and Isomerism
Types of Structural Isomerism
There are three types of structural isomerism existing, namely chain isomerism, position isomerism and functional group isomerism.
- Chain Isomerism: Chain isomerism occurs when there is a difference in the atomic arrangement of the carbon to the carbon chain of a molecule. If two or more compounds have the same type of molecular formula with different main chains, then they are said to exhibit the property of chain isomerism. This phenomenon is also called skeletal isomerism.
- Position Isomerism: Positional isomerism arises when there is a difference in the positions occupied by the substituent atoms or a group of atoms or due to the unsaturation occurring in the chain. When the position of the functional groups with respect to the main chain atom changes, the phenomenon is called position isomerism.
- Functional Group Isomerism: Functional group isomerism occurs when there is a presence of an odd form of functional groups with the same chemical formula. When some compound has two different structures but the same chemical formula, then it is said to exhibit functional isomerism.