Learning Objective How to name aldehydes and ketones. A carbonyl group consists of a carbon atom double-bonded to an oxygen atom, written as C=O . Aldehydes and ketones are two compounds which contain the carbonyl group. Aldehydes and ketones are constitutional isomers . For example, the aldehyde and ketone below both have the molecular formula C 3 H 6 O. The simplest aldehyde is methanal, commonly known as formaldehyde, and used as a preservative. The name of this molecule is butanal. Practice Questions 1. What is the name of Molecule A? 2. This molecule is named 5-methylhexanal. Number the carbons. 3. Number the carbons. What is the name of Molecule B? 4. This molecule is named 3-ethyl-4-methylhexanal. Number the carbons. 5. Number the carbons. What is the name of Molecule C? 6. This molecule is named 3-pentenal. Number the carbons. 7. Number the carbons. What is the name of Molecule D? 8. A well-known ketone is 2-propanone, commonly known as acetone, and used as a nail polish remover. This molecule is named 2-pentanone. What is the name of Molecule E? 9. The name of this molecule is 5-ethyl-2-heptanone. Number the carbons. 10. Number the carbons. What is the name of Molecule F? 11. This molecule is named 6-chloro-4-ethyl-3-heptanone. Number the carbons. 12. Number the carbons. What is the name of Molecule G? 13. The name of this molecule is 3-bromocyclohexanone. Number the carbons. 14. Number the carbons. What is the name of Molecule H? 15. The name of this molecule is 4-hydroxy-2-butanone. Number the carbons. 16. Number the carbons. What is the name of Molecule I? 17. This molecule is named 5-chloro-4-oxohexanal. Number the carbons. 18. Number the carbons. What is the name of Molecule J? 19. What additions do we make to our existing naming rules to name aldehydes and ketones? 20. Write the steps that you use to name an aldehyde or ketone in order, as instructions for a student who doesn't know how to do it. 21. Draw any aldehyde or ketone and go through the steps in naming your molecule.