In organic chemistry, isomers are molecules that have the same molecular formula but different arrangements of atoms in space. There are two main types of isomers: structural isomers and stereoisomers.1. Structural isomers also known as constitutional isomers are molecules with the same molecular formula but different connectivity of atoms. In other words, the atoms are bonded together in a different order. This leads to differences in physical and chemical properties of the isomers.Example: C4H10 has two structural isomers: butane and isobutane or 2-methylpropane .Butane:H H H H| | | |H-C-C-C-C-H | | | | H H H HIsobutane 2-methylpropane : H H H | | |H H-C-C-C-H | | | H H HIn this example, both butane and isobutane have the same molecular formula C4H10 , but the connectivity of the carbon atoms is different, leading to different structures and properties.2. Stereoisomers are molecules with the same molecular formula and connectivity of atoms but different spatial arrangements of the atoms. Stereoisomers can be further divided into two subcategories: enantiomers and diastereomers.Enantiomers are non-superimposable mirror images of each other, like left and right hands. They have the same physical properties but differ in the way they interact with plane-polarized light and other chiral molecules.Diastereomers are stereoisomers that are not mirror images of each other. They have different physical and chemical properties.Example: C4H8O2 has two stereoisomers: R - and S -lactic acid. R -lactic acid: H O |H-C-C-O-H | C-H | H S -lactic acid: H O |H-C-C-O-H | C-H | HIn this example, both R - and S -lactic acid have the same molecular formula C4H8O2 and connectivity, but the spatial arrangement of the atoms around the chiral center the carbon atom bonded to the hydroxyl group is different. These two isomers are enantiomers.In summary, the key differences between structural isomers and stereoisomers are:- Structural isomers have the same molecular formula but different connectivity of atoms, leading to different structures and properties.- Stereoisomers have the same molecular formula and connectivity but different spatial arrangements of atoms, leading to different interactions with plane-polarized light and other chiral molecules for enantiomers or different physical and chemical properties for diastereomers .