Chemistry » Organic Molecules » IUPAC Naming And Formulae

Naming Carbonyl Compounds

Naming carbonyl compounds

A carbonyl group consists of a carbon atom that is bonded to an oxygen atom through a double bond (C\(=\)O). There are many different functional groups that contain a carbonyl group.

Naming aldehydes

If the carbonyl group is on the end of the carbon chain, the organic compound is called an aldehyde. An aldehyde has the suffix -al.

Example:

Question

Give the IUPAC name and molecular formula for the following organic compound

Naming Carbonyl Compounds

Identify the functional group

The compound has a C\(=\)O (carbonyl) group and no other functional groups. It is therefore either an aldehyde or a ketone. The carbonyl group is on the last (terminal) carbon in the main chain so the compound is an aldehyde. It will have the suffix -al.

Find the longest carbon chain containing the functional group

There are three carbons in the longest chain that contains the functional group. The prefix for this compound will be prop-. As there are only single bonds between the carbon atoms, the prefix becomes propan-.

Number the carbon atoms in the carbon chain

The carbon atoms will be numbered so that the carbon atom of the aldehyde group has the lowest number possible. In this case that is from right to left.

Look for any branched groups

There are no branched groups in this compound.

Combine the elements of the compound’s name into a single word in the order of branched groups; prefix; name ending according to the functional group

The compound’s name is propanal (there is no need to say propan-1-al as by definition all aldehydes are -1-al).

Reduce the structural representation to the molecular formula

There are 3 carbon atoms, 6 hydrogen atoms and 1 oxygen atom so the molecular formula is \(\text{C}_{3}\text{H}_{6}\text{O}\).

(Remember that there is no structural information given by the molecular formula)

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