1.2 Alkenes and Alkynes

  • Unsaturated hydrocarbons: molecules in which at least one Carbon – Carbon bond is a double or triple bond.

    • Hydrogen = syrup
    • Carbon = pancake
    • Saturated pancakes = alkanes

    Hydrocarbons

  • Alkenes: hydrocarbons with at least one double bond between carbons and end with “one”

    • CnH2n

    Alkane, Alkene, Alkynes

  • Alkynes: hydrocarbons with at least one triple bond between carbons and end with “yne”

    • CnH2n-2

Naming Alkenes and Alkynes

  • Parent chain must include double / triple bond. Trumps the longest chain rule.
    • A chain with multiple double/triple bond would go: octa-2,4,6-triene.
  • Number chain with lowest number for substituent groups
  • Name substituents as usual but indicate bond type and place of bond
  • Note: you ignore the number of carbon only if the name will not change no matter where you draw the double/triple bond.

Stereoisomers

  • same chemical formula and structural backbone but different arrangement of atoms in space

  • Cis/Trans isomers are stereoisomers which occur only with alkenes

    • Cis: the group of interest are located on the same plane of the double bond.
    • Trans: the groups of interest are located on opposing planes of the double bond.