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1.5: Halogens

  • Page ID
    222788
  • Learning Objective

    • How to name halogenated hydrocarbons

    The halogens are elements belonging to Group 7A. Fluorine, chlorine, bromine, and iodine can be added to hydrocarbons through reactions with their diatomic forms or when bound to hydrogen as hydrogen halides.

    Figure \(\PageIndex{1}\).svg
    Figure \(\PageIndex{1}\). where X is any halogen atom:Diatomic halogen vs halogen halide

    When a halogen atom is bound to an otherwise saturated carbon atom, the molecule is known as an alkyl halide.

    Substituent Symbol Name
    Fluorine Fl fluoro-
    Chlorine Cl chloro-
    Bromine Br bromo-
    Iodine I iodo-

    When naming molecules according to the IUPAC system of nomenclature, remember prefix-parent-suffix (like un-believe-able).

    • prefix: what are the substituents?
    • parent: how many carbons?
    • suffix: what is the family of compounds?

    Practice Questions

    1. This molecule is named 2-chlorobutane.

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

    What is the name of Molecule A?

    Figure \(\PageIndex{3}\).svg
    Figure \(\PageIndex{3}\): Molecule A

    2. This molecule is named 2-fluoro-3-methylpentane.

    Figure \(\PageIndex{4}\).svg
    Figure \(\PageIndex{4}\): 2-fluoro-3-methylpentane

    This molecule is named 4-iodo-2-methylhexane.

    Figure \(\PageIndex{5}\).svg
    Figure \(\PageIndex{5}\): 4-iodo-2-methylhexane

    What is the name of Molecule B?

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

    3. This molecule is named 1-chloro-2-butene.

    Figure \(\PageIndex{7}\).svg
    Figure \(\PageIndex{7}\): 1-chloro-2-butene

    This molecule is named 5-fluoro-2-hexene.

    Figure \(\PageIndex{8}\).svg
    Figure \(\PageIndex{8}\): 5-fluoro-2-hexene

    What is the name of Molecule C?

    Figure \(\PageIndex{9}\).svg
    Figure \(\PageIndex{9}\): Molecule C

    4. This molecule is named 5-fluoro-1,3-cyclohexadiene.

    Figure \(\PageIndex{10}\).svg
    Figure \(\PageIndex{10}\): 5-fluoro-1,3-cyclohexadiene

    What is the name of Molecule D?

    Figure \(\PageIndex{11}\).svg
    Figure \(\PageIndex{11}\): Molecule D

    5. Write the steps that you use to name an alkyl halide, in order, as instructions for a student who doesn't know how to do it.

    6. Draw any alkyl halide and go through the steps in naming your molecule.

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