What is chain isomerism in relation to organic molecules?

1 Answer
Jan 14, 2017

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_9ClC4H9Cl then we could have a straight chain with the chlorine on the end carbon: 1-chlorobutane CH_3CH_2CH_2CH_2ClCH3CH2CH2CH2Cl or we could have the chlorine on one of the middle carbons: 2-chlorobutane CH_3CH_2CHClCH_3CH3CH2CHClCH3. These are positional isomers.

Alternatively, we might have a branched chain, 1-chloromethylpropane: (CH_3)_2CHCH_2Cl(CH3)2CHCH2Cl. This is a chain isomer of 1-chlorobutane, where the carbon skeleton of the molecule is configured differently.