It is a phenomenon in which two or more compounds share the same chemical formula but have different structural formula and properties. This is primarily due to variations in structural or spatial arrangements.
Types of Isomerism:
Structural Isomerism
Stereo Isomerism
Structural Isomerism:
Isomers are molecules that share the same chemical formula but are organized differently in space. This rules out any unique configurations induced by the molecule rotating as a whole or around individual bonds. There are numerous more ways in which this molecule could twist itself. All carbon-carbon single bonds allow for total free rotation. If you had a model of a molecule in front of you, you'd have to disassemble and reconstruct it to create an isomer of that molecule. If you can create an ostensibly distinct molecule just by twisting single bonds, it is not different; it is still the same. In structural isomerism, the atoms are organized in a whole different order. 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 a sort of structural isomerism in which a piece of a hydrocarbon skeleton (a string of carbons with hydrogen atoms attached) is positioned differently than the remainder of the carbon backbone.
In organic chemistry, a zigzag line indicates the carbon backbone. Each zigzag vertex represents a carbon atom with enough hydrogen atoms attached to complete an octet. Elements other than hydrogen bonded to the carbon backbone are represented by element symbols.
For example, there are two structural isomers of the chemical formula C3H7Br. In one of them, the bromine atom is near the end of the chain, whereas in the other it is in the center.
Functional group isomerism:
Structural isomers that are functional are those that share the same chemical formula, or the same number of atoms of the same elements, but differ in how the atoms are joined, resulting in distinct groupings. These atomic groups are referred to as functions or functional groups.
The combination of the alcohol ethanol (H3C–CH2–OH) and the ether dimethyl ether (H3C–O–CH2H) is one example. On the other hand, since they are both alcohols and share the same major functional group (the hydroxyl -OH), 1-propanol and 2-propanol are structural isomers but not functional isomers.
Metamerism isomerism:
When there are distinct alkyl chains on either side of the functional group, an analogous kind of isomerism takes place. This rare kind of isomerism is usually observed in compounds that include an alkyl group around a divalent element (like oxygen or sulfur).
Dimethyl ether (C2H5-O-C2H5) and methyl propyl ether (CH3-O-CH2-CH2-CH3) are two examples.
Position Isomerism:
In position isomers, the functional groups or substituent atoms are positioned differently. The attachment of the functional groups to various carbon atoms in the carbon chain is usually the cause of this isomerism. For instance: First and second chloropropane
One chlorine atom is present in 1-chloropropane at the first carbon, while another chlorine atom is present in 2-chloropropane at the second carbon.
Tautomerism:
Tautomerism is a dynamic equilibrium between two molecules with identical chemical formulas. A tautomer of a chemical is an isomer that differs solely in the positions of protons and electrons. Typically, the tautomers of a chemical exist in equilibrium and can easily interchange. It occurs through an intramolecular proton transfer. The most prevalent type of tautomerism is keto-enol tautomerism. A carbonyl molecule with at least one α-hydrogen atom is transformed to an enol by transferring the α-hydrogen onto the oxygen atom.
Ring Chain Isomerism:
Ring chain isomers are compounds with the same chemical formula but cyclic and open chain structures; this phenomenon is known as ring-chain isomerism. Ring chain isomers include propene and cyclopropane, for instance.
Stereoisomerism:
Compounds with the same chemical formula but different relative atom orientations or positions in space are said to exhibit stereoisomerism. The substances that display stereoisomerism are called stereoisomers. Stereoisomerism can be further divided into:
• Geometric isomerism: It is exhibited by molecules that have double bonds or ring structures that lock their spatial positions to one another.
• Optical Isomerism: Optical isomers are two or more compounds with the same chemical structure but different optical activities.