constitutional isomerism

Constitutional isomers are molecules that share the same chemical formula but have different atom connectivity. They possess the same components but are arranged differently, leading to distinct chemical and physical properties. For instance, butane (C₄H₁₀) exists as two constitutional isomers: n-butane, with a continuous carbon chain, and isobutane, with a branched structure.12

While simple hydrocarbons like methane and ethane have no constitutional isomers, the number of possible isomers increases significantly with more atoms. For example, there are 366,319 constitutional isomers for a hydrocarbon with 20 carbon atoms. This phenomenon is a fundamental concept in chemistry, illustrating how variations in atomic arrangement can create entirely different compounds.13