2-pentene and 2-methyl-1-butene exhibit positional isomerism, which is a type of structural isomerism. In positional isomers, the molecular formula is the same, but the position of the functional group or substituent differs.2-pentene has the molecular formula C5H10 and contains a carbon-carbon double bond C=C at the second carbon atom in the chain. Its structure can be represented as CH3-CH=CH-CH2-CH3.2-methyl-1-butene also has the molecular formula C5H10, but the carbon-carbon double bond C=C is at the first carbon atom in the chain, and there is a methyl group CH3 attached to the second carbon atom. Its structure can be represented as CH2=C CH3 -CH2-CH3.In summary, the structural difference between these two positional isomers lies in the location of the double bond and the methyl group within the carbon chain.