Isomerism is a phenomenon in which two or more compounds have the same chemical formula but possess different properties because of different structural or spatial arrangements. Compounds which exhibit isomerism are called isomers. There are two types of isomerism:
- Structural isomerism
The compounds which exhibit this type of isomerism have the same molecular formula but different structures, as in how they are linked to each other. Structural isomerism is further classified into
- Chain isomerism
- Position isomerism
- Functional group isomerism
Chain isomerism: The phenomenon is termed as chain isomerism when two or more compounds have the same molecular formula but differ in the branching of carbon atoms. These compounds are called chain isomers. Example C5H12 can be represented as three compounds.
Position isomerism: The isomerism in which two or more compounds differ in the position of functional group or substituent atoms is called position isomerism. Example: C3H7OH can be represented in two arrangements.
Functional isomerism: The isomerism in which two or more compounds have identical molecular formula but differ in the functional group present is called functional isomerism and these isomers are called functional isomers. Example C3H6O can be represented as a ketone and as an aldehyde.
Metamerism: This isomerism is exhibited by compounds due to the presence of different alkyl chains on either sides of the functional group.Example:C4H10O can be represented as ethoxyethane (C2H5OC2H5) and methoxypropane (CH3OC3H7)
Stereoisomerism is a phenomenon in which compounds have the same molecular formula but differ in the relative positioning or orientation of atoms in space. The compounds which exhibit this type of isomerism are called as stereoisomers. These are further classified into:
- Geometrical isomerism
- Optical isomerism
Geometric isomerism: This is being exhibited by molecules in which their special positions are locked to each other due to the presence of a ring structure or a double bond.
Optical isomerism: The isomerism exhibited by two or more compounds which have the same molecular arrangement but differ in the optical activity.
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