Isomerism of Functional Groups

Structural isomers are organic compounds with the same molecular formula but different structures. Structural isomerism can be simplified into positional, chain and functional isomers.

A position isomer is when a functional group can be located in different positions along the chain. This occurs for alcohols, amines and ketones. As a result, the structure and name of the organic compound will change.

Chain isomerism occurs by altering the length of the parent chain. For instance, pentanol can be shortened to 2-methylbutan-1-ol or dimethylpropanol whilst maintaining the same molecular formula of C5H12O.

Functional group isomerism is when one functional group has the same molecular formula as another functional group. There are two pairs of groups that share the same molecular formulas: aldehydes and ketones (CnH2nO), and carboxylic acids and esters (CnH2nO).

If we consider aldehydes and ketones, the molecular formula C4H8O produces the following three isomers:

And if we consider carboxylic acids and esters, the molecular formula C3H6O2 produces the following three isomers:

Naming Organic Compounds | Elucidate Video

In the video below, Henry goes over the IUPAC naming conventions for organic compounds and offers some tips for solving chemistry exam questions.