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

• Alkenes: hydrocarbons with at least one double bond between carbons and end with “one”
    * CnH2n

• 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.

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