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1.9: Aldehydes and Ketones

  • Page ID
    222813
  • 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.

    Figure \(\PageIndex{1}\).svg
    Figure \(\PageIndex{1}\). The R group can also be a hydrogen: aldehyde
    Figure \(\PageIndex{2}\).svg
    Figure \(\PageIndex{2}\). The R groups can be the same or different: ketone

    Aldehydes and ketones are constitutional isomers. For example, the aldehyde and ketone below both have the molecular formula C3H6O.

    Figure \(\PageIndex{3}\).svg
    Figure \(\PageIndex{3}\): C3H6O

    The simplest aldehyde is methanal, commonly known as formaldehyde, and used as a preservative.

    Figure \(\PageIndex{4}\).svg
    Figure \(\PageIndex{4}\): methanal

    The name of this molecule is butanal.

    Figure \(\PageIndex{5}\).svg
    Figure \(\PageIndex{5}\): butanal

    Practice Questions

    1. What is the name of Molecule A?

    Figure \(\PageIndex{6}\).svg
    Figure \(\PageIndex{6}\): Molecule A

    2. This molecule is named 5-methylhexanal. Number the carbons.

    Figure \(\PageIndex{7}\).svg
    Figure \(\PageIndex{7}\): 5-methylhexanal

    3. Number the carbons. What is the name of Molecule B?

    Figure \(\PageIndex{8}\).svg
    Figure \(\PageIndex{8}\): Molecule B

    4. This molecule is named 3-ethyl-4-methylhexanal. Number the carbons.

    Figure \(\PageIndex{9}\).svg
    Figure \(\PageIndex{9}\): 3-ethyl-4-methylhexanal

    5. Number the carbons. What is the name of Molecule C?

    Figure \(\PageIndex{10}\).svg
    Figure \(\PageIndex{10}\): Molecule C

    6. This molecule is named 3-pentenal. Number the carbons.

    Figure \(\PageIndex{11}\).svg
    Figure \(\PageIndex{11}\): 3-pentenal

    7. Number the carbons. What is the name of Molecule D?

    Figure \(\PageIndex{12}\).svg
    Figure \(\PageIndex{12}\): Molecule D

    8. A well-known ketone is 2-propanone, commonly known as acetone, and used as a nail polish remover.

    Figure \(\PageIndex{13}\).svg
    Figure \(\PageIndex{13}\): 2-propanone

    This molecule is named 2-pentanone.

    Figure \(\PageIndex{14}\).svg
    Figure \(\PageIndex{14}\): 2-pentanone

    What is the name of Molecule E?

    Figure \(\PageIndex{15}\).svg
    Figure \(\PageIndex{15}\): Molecule E

    9. The name of this molecule is 5-ethyl-2-heptanone. Number the carbons.

    Figure \(\PageIndex{16}\).svg
    Figure \(\PageIndex{16}\): 5-ethyl-2-heptanone

    10. Number the carbons. What is the name of Molecule F?

    Figure \(\PageIndex{17}\).svg
    Figure \(\PageIndex{17}\): Molecule F

    11. This molecule is named 6-chloro-4-ethyl-3-heptanone. Number the carbons.

    Figure \(\PageIndex{18}\).svg
    Figure \(\PageIndex{18}\): 6-chloro-4-ethyl-3-heptanone

    12. Number the carbons. What is the name of Molecule G?

    Figure \(\PageIndex{19}\).svg
    Figure \(\PageIndex{19}\): Molecule G

    13. The name of this molecule is 3-bromocyclohexanone. Number the carbons.

    Figure \(\PageIndex{20}\).svg
    Figure \(\PageIndex{20}\): 3-bromocyclohexanone

    14. Number the carbons. What is the name of Molecule H?

    Figure \(\PageIndex{21}\).svg
    Figure \(\PageIndex{21}\): Molecule H

    15. The name of this molecule is 4-hydroxy-2-butanone. Number the carbons.

    Figure \(\PageIndex{22}\).svg
    Figure \(\PageIndex{22}\): 4-hydroxy-2-butanone

    16. Number the carbons. What is the name of Molecule I?

    Figure \(\PageIndex{23}\).svg
    Figure \(\PageIndex{23}\): Molecule I

    17. This molecule is named 5-chloro-4-oxohexanal. Number the carbons.

    Figure \(\PageIndex{24}\).svg
    Figure \(\PageIndex{24}\): 5-chloro-4-oxohexanal

    18. Number the carbons. What is the name of Molecule J?

    Figure \(\PageIndex{25}\).svg
    Figure \(\PageIndex{25}\): 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.

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