Alkenes 3.4

• Steroisomerism

  Sereoisomers have the same structural formulae but have different spatial arrangement of atoms.
• When does E-Z stereoisomerism occur

  When there is restricted rotation around the C=C bond.

  When There are two different groups/atoms attached both ends of the double bond
• What is an electrophile

  An electron pair acceptor.
• Addition reaction

  A reaction where two molecules react together to produce one.
• Reaction of bromine with alkenes.

  Change in functional group: Alkene -> dihalogenalkane.

  Regent: Bromine.

  Conditions: Room Temperature, aqueous

  Type of Regent: Electrophile Br+
• Why is a Br-Br bond polar

  Br2 is polarised as the electrons in the double bonds repel the electron pair in the Br-Br bond. This induces a dipole.
• Reaction of hydrogen Bromide with alkenes.

  Change in functional group: Alkene -> Halogenalkane.

  Reagent: Hbr

  Conditions: Room temperature.

  Type of Reagent: Electrophile H+
• Why is the H-Br bond polar

  Br is more electronegative than H. The H is thus attracted to the electron-rich double bond.
• Whats Markownikoff's rule?

  In most cases, bromine will be added to the carbon with the fewest hydrogens attached to it.
• Structural formula

  Molecules with the same molecular formular but a different structual formula.
• Polymer

  A long unit composed of many repeating smaller units.
• Monomer

  Small basic molecules which can react together and bond with other similar molecules to form polymers.
• Addition polymerisation

  A process where many small molecules join together by breaking their double bonds and forming long chains without the loss of any atoms
• Reaction of sulfuric acid with alkenes

  Change in functional group: Alkene -> Alkyl hydrosulfate.

  Reagents: Concentrated H2SO4, Cold.

  Mechanisms: Electrophilic addition.

  Type of Reagent: Electrophile, H2SO4
• Why are poly(alkenes) like alkanes unreactive

  Due to their strong C-C and C-H bonds.