Question

What is chain isomerism in relation to organic molecules?

Answer 1

Chain isomerism relates to molecules with the same molecular formula but different carbon skeleton.

Positional isomerism relates to molecules with the same carbon skeleton but functional groups in different positions.

Explanation:

If we consider `C_4H_9Cl` then we could have a straight chain with the chlorine on the end carbon: 1-chlorobutane `CH_3CH_2CH_2CH_2Cl` or we could have the chlorine on one of the middle carbons: 2-chlorobutane `CH_3CH_2CHClCH_3`. These are positional isomers.

Alternatively, we might have a branched chain, 1-chloromethylpropane: `(CH_3)_2CHCH_2Cl`. This is a chain isomer of 1-chlorobutane, where the carbon skeleton of the molecule is configured differently.