Isomerism is a phenomenon where two or more organic compounds have the same molecular formula but different structures or arrangements of atoms. This results in different physical and chemical properties. There are two main types of isomerism: structural isomerism and stereoisomerism.1. Structural Isomerism: Structural isomers have the same molecular formula but different structural arrangements of atoms. There are several types of structural isomerism:a Chain Isomerism: This occurs when the carbon atoms in a molecule are arranged in different ways, forming straight or branched chains. For example, butane C4H10 has two chain isomers: n-butane straight chain and isobutane branched chain .b Position Isomerism: This occurs when a functional group or substituent is attached to different positions on the same carbon chain. For example, propanol C3H8O has two position isomers: 1-propanol OH group on the first carbon and 2-propanol OH group on the second carbon .c Functional Group Isomerism: This occurs when two or more compounds have the same molecular formula but different functional groups. For example, C2H6O can represent either ethanol alcohol functional group or dimethyl ether ether functional group .d Ring-Chain Isomerism: This occurs when compounds have the same molecular formula but differ in whether they form a ring or a chain structure. For example, C4H8 can represent either cyclobutane ring structure or but-1-ene chain structure .2. Stereoisomerism: Stereoisomers have the same molecular formula and the same structural arrangement of atoms, but they differ in the spatial arrangement of atoms. There are two types of stereoisomerism:a Geometric Isomerism cis-trans isomerism : This occurs when two or more compounds have the same molecular formula and structural arrangement but differ in the spatial arrangement of atoms around a double bond or a ring structure. For example, in 2-butene C4H8 , there are two geometric isomers: cis-2-butene both methyl groups on the same side of the double bond and trans-2-butene methyl groups on opposite sides of the double bond .b Optical Isomerism enantiomerism : This occurs when two or more compounds have the same molecular formula and structural arrangement but differ in the spatial arrangement of atoms around a chiral center a carbon atom with four different groups attached . These isomers are non-superimposable mirror images of each other and are called enantiomers. For example, in 2-chlorobutane C4H9Cl , there are two optical isomers: R -2-chlorobutane and S -2-chlorobutane.In summary, isomerism in organic compounds can be broadly classified into structural isomerism and stereoisomerism, with several subtypes in each category. These isomers have different physical and chemical properties, making the study of isomerism essential in understanding the behavior of organic compounds.