ALKENES, POLYMERS AND ALCOHOLS

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  • ALKENES, POLYMERS & ALCOHOLS
    • ALKENES
      • have a double carbon bond so are unsaturated
      • general formula: CnH2n
      • 1. Ethene C2H4 2.Propene C3H6 3.Butene C4H8
      • isomers
        • but-1-ene and but-2-ene are isomers -> 2 different structures as double bond can be in 2 different places
        • two molecules with identical molecular formula but different structures
    • HALOALKANES
      • halogens react with alkenes to form haloalkanes
      • addition reactions
        • when double carbon bond splits and a halogen atom is aded to each of the carbons
        • bromine + ethene -> dibromethene. C2H4 +Br2 -> C2H4Br2
      • reaction between bromine and alkenes
        • when shaken, orange bromine molecules react with the alkene to make the colourless dibromoalkAne
    • ADDITION POLYMERISATION
      • high pressure + catalyst + small molecules open up double bonds an polymerise to form polymers (very long saturated chains)
      • monomer is added to the chain each time
      • can be written as an equation using repeating units
        • bond always comes out either side of the brackets
        • monomer can be found by taking repeat unit and adding a double bond
    • USES
      • polyethene
        • light structure -> packaging
      • polychloroethene
        • insulating electrical cables, clothes, pipes
    • BIODEGRADABILITY
      • don't degrade: unreactive to chemicals + bacteria
      • can recycle (high cost) or incinerate (produces toxic fumes)
      • polylactic acid (PLA) = biodegradable polymer ->special links are attacked by chemicals and absorb UV to break it down into its original monomers
    • ALCOHOLS
      • part of the homologous series
      • remove hydrogen atom in an alkAne by an -OH
      • 1. methanol 2.ethanol 3,propanol 4.butanol 5.pentanol
    • CONDENSATION POLYMERS
      • 2 different types of monomer = polymer chains
      • produces a small molecule + polymer
      • monomer + monomer -> condensation polymer + water
    • DEHYDRATION OF ETHANOL TO ETHENE
      • water molecule removes from the alcohol
      • ethanol vapour passed over catalyst aluminium oxide (which provides large SA)
      • C2H5OH  -> C2H4 +H2O

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