Alkenes

• Define Alkenes:

  A hydrocarbon chain that contains at least one double bonded carbon atoms
• The formula for Alkenes:

  CnH2n
• The suffix for an alkene with two double bonds:

  diene
• The stem of an alkene with two double bonds has an extra ' a '
• Are Alkenes saturated or unsaturated?

  unsaturated
• There are no possible isomers of the alkenes until the alkene...

  Butene
• What are C=C double bonds made up of?

  • sigma bond
  • pi bond
• Define Pi bond (π-bond):

  A type of covalent bond formed by the adjacent p orbital overlapping sideways above and below the same plane of a sigma bond
• Which type of bond in C=C double bonds are weaker?

  Pi bonds
• Can π-bonds rotate?

  No
• Can σ-bonds rotate?

  Yes
• Pi bonds can only be made after a sigma bond is formed
• Why can't double bonds rotate?

  Pi bonds overlap sideways above and below the same plane of a sigma bond, this means the electron density is spread out which locks the carbon atoms in position
• What shape and bond angle does each carbon at in a double bond have?

  Trigonal planar, 120 °
• Which are more reactive, alkanes or alkenes?

  Alkenes
• What is used to test for alkenes and other unsaturated compounds?

  Bromine water
• How do you test for an unsaturated compound?

  Bromine water changes from brown-orange to colourless
• Define a Catalyst:

  A substance that increases the rate of reaction without being used up by providing an alternative pathway with a lower activation energy
• Outline why alkenes are more reactive than alkanes?

  • high electron density of double bond and electron cloud of pi bond
  • pi bonds require less energy to break
• State why are alkenes not soluble in water?

  nonpolar bonds
• Define Electrophile:

  An electron pair acceptor
• What attracts electrophiles to alkenes?

  The high electron density of the electron cloud of a pi bond
• Alkenes undergo what type of addition reaction?

  Electrophilic addition
• Name the four addition reactions alkenes undergo:

  • Hydrogenation
  • Halogenation
  • Hydration
  • Addition of hydrogen halides
  • Addition of concentration sulfuric acid
• State the conditions needed for hydration (the addition of steam to an alkene):

  • acid catalyst
  • 300℃
  • 6079.5 kPa
• Name this molecule:

  Dihydrogen phosphate ion

  
• What process causes a partially positive hydrogen atom to break the covalent bond from the partially negative oxygen atom in a hydroxyl group so that it can bond to an alkene?

  Heterolytic fission
• The positive hydrogen atom that bonds to an alkene is called...?

  Electrophile
• What is this molecule called?

  Carbocation

  
• What is this molecule called?

  Phosphoric acid

  
• Alkene + Water --acid catalyst,300 °C,6079.5kPa--> alcohol
• Alkene + Water -- acid catalyst,300 °C,6079.5kPa --> alcohol
• Alkene + Water -- acid catalyst,300°C,6079.5kPa --> alcohol
• Alkene + Water -- acid catalyst,300°C,6079.5kPa --> alcohol
• What does the acid catalyst give to the alkene?

  hydrogen ion (Proton)
• What is the formula for phosphoric acid?

  H3PO4
• A carbocation has a lone pair of electrons on a carbon atom in the compound
• CnH2n (g) + H2O (g) -- H+, 300 °C, 6079.5kPa --> CnH2n+1OH (g)
• CnH2n (g) + H2O (g) -- H+, 300 °C, 6079.5kPa --> CnH2n+1OH (g)
• CnH2n (g) + H2O (g) -- H+, 300 °C, 6079.5kPa --> CnH2n+1OH (g)