3.5 Naming Aldehydes and Ketones

When naming aldehydes, we follow the rules for naming alkanes with the addition of two rules:

  • 1. We number the parent chain in the direction that gives highest priority (lowest number) to the aldehyde (carbonyl) carbon.
  • 2. We replace “e” with “al”.

When naming ketones, we follow the same rules for naming alkanes, except:

  • 1. Similar to aldehydes, the parent chain must be chosen with priority given to the ketone (carbonyl) carbon.
  • 2. Replace the “e” with “one”.
  • 3. The carbonyl carbon in a cyclic ketone is assumed to be the #1 carbon.

Note: it is also possible to name each chain on either side and then follow it with the word “ketone”. For example: 3-hexanone can also be called ethyl propyl ketone.