There are two main types of isomers:
- Structural isomers: Structural isomers have the same molecular formula, but different arrangements of atoms within the molecule. These isomers may have different physical and chemical properties due to the different ways in which the atoms are bonded together. For example, n-pentane and isopentane are structural isomers with the same molecular formula (C5H12), but different structures.
- Stereoisomers: Stereoisomers have the same molecular formula and the same atom-to-atom connections, but differ in the spatial arrangement of the atoms. Stereoisomers can be further divided into two subtypes:
a) Geometric isomers (also known as cis-trans isomers): Geometric isomers have the same atom-to-atom connections, but differ in the orientation of functional groups around a double bond or a ring structure. For example, cis-2-butene and trans-2-butene are geometric isomers with the same molecular formula and the same atom-to-atom connections, but different spatial arrangements.
b) Optical isomers (also known as enantiomers): Optical isomers are mirror images of each other and cannot be superimposed on each other. They have the same molecular formula, the same atom-to-atom connections, but differ in the spatial arrangement of atoms or functional groups around a chiral center. Optical isomers may have different physical and chemical properties and interact differently with other molecules. An example of optical isomers is L- and D-glucose.