Tools of the trade: understanding functional groups and naming compounds
To categorise the vast number of organic compounds we divide them into functional groups – these are groups of atoms that give the molecule characteristic chemical properties. For example, in ethanol, the –OH group is called a hydroxyl functional group, which is present in a family of compounds called alcohols. The carbonyl group between two carbons is called a ketone, whereas when it is between a carbon atom and hydrogen it is an aldehyde. Notice how the functional group is reflected in the name of the compound, for example, propanone for a ketone.
Also, the name specifies the length of the carbon chain – for propanone there are three carbons.
Naming straight-chain alkyl groups
When naming compounds, chemists like to use abbreviations. The same rules are followed when naming compounds – this is called IUPAC naming – and this helps chemists to be able to draw a compound from its name, without having to look up the structure.
Shown below are the IUPAC names for chains of carbon atoms, called alkyl groups, from a one-carbon chain to a four-carbon chain.
Compounds with similar structures and the same functional group, or groups, have similar properties. Organic chemists study the structure and reactivity of organic compounds, so drawing accurate structures and recognising functional groups is crucially important.
As well as the images that appear on this page, see below for some functional group posters that we hope will be useful to you as you work through the course content.
If you would like some further information on recognising functional groups you may find this YouTube clip of use.
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