The isomerism that exists between CH3CHCl2 and CH2ClCH2Cl is which type?

• A. Chain isomerism
• B. Positional isomerism
• C. Functional group isomerism
• D. Metamerism

Answer: (B)

Positional isomerism is being tested here. Both compounds have the same two-carbon chain and the same kinds of atoms, but the chlorine atoms occupy different locations along that chain. In the first molecule, both chlorines are attached to the same carbon, while in the second molecule, a chlorine sits on each carbon. Since the carbon framework is unchanged and only the placement of substituents differs, they are positional isomers. It’s not chain isomerism because the skeleton hasn’t changed, not functional group isomerism because the same functional groups are present, and not metamerism, which involves different alkyl groups around a functional group.