In the study organic chemistry we come across many cases when two or more compounds consist of equal number of like atoms. These compounds have the same molecular formula but differ from each other in physical or chemical properties, and are called Isomers and the Phenomenon is called Isomerism. Since isomers have an equivalent molecular formula, the distinction in their properties should flow from to totally different modes of combination or arrangement of atoms at intervals the molecule. There are two main types isomerism:
- Structural Isomerism
When the isomerism is due to difference in the arrangement of atoms within the molecule, without any reference to space, the phenomenon is called Structural Isomerism. In other words, Structural isomers are compounds that have the same molecular formula but different structural formulas. Structural isomerism is of five types:
- Chain Isomerism
- Position Isomerism
- Functional Isomerism
When isomerism is caused by the different arrangement of atoms or group is space, the phenomenon is called stereoisomerism. The stereoisomers have the same structural formulas but differ in arrangement of atoms is space. In different words, stereoisomerism is exhibited by such compounds that have constant molecular formula however take issue in configuration. (The term compounds). Stereoisomerism is of two types:
- Geometrical or Cis-Trans Isomerism.
- Optical Isomerism.