Alkenes and Alkynes Overview

Alkenes

  • Definition: Unsaturated hydrocarbons containing one or more double bonds between carbon atoms.
  • General Formula: For alkenes with one double bond: CnH{2n}.
  • Examples:
    • Ethene: C2H4
    • Propene: C3H6
    • 1-Butene: C4H8
    • 2-Butene: C4H8.
  • Naming: Change the -ane ending of corresponding alkanes to -ene. Specify the location of double bonds for alkenes with four+ carbons.
  • Cyclic Alkenes: Carbon 1 is one of the carbons in the double bond.

Alkynes

  • Definition: Unsaturated hydrocarbons containing one or more triple bonds.
  • Naming: Similar to alkenes, except names end in -yne.
  • Reactivity: Generally more reactive than alkenes due to higher electron density from triple bonds.

Properties of Alkenes & Alkynes

  • Nonpolar, low solubility in water, low melting/boiling points.
  • More reactive than alkanes due to double or triple bonds.
  • Alkynes are usually more reactive than alkenes.

Quiz Review Points

  1. Alkenes cannot be saturated.
  2. Correct structures include specifications for naming based on IUPAC rules.
  3. Low solubility and melting points are properties shared with alkenes and alkynes.