Polymer Revolution

Polymer Revolution

1. Addition Reactions of Alkenes

   • Alkenes are UNSATURATED HYDROCARBONS
     • Cn H2n
     • Double bond
     • Two double bonds = -diene
   • Test for unsaturation = Bromine water - red/brown to colourless (dibromoalkane)
     • Example of electrophillic addition
   • Producing alkanes
     • Add Hydrogen
     • Nickel catalyst at 150C and high pressure OR platinum catalyst at room temperature and pressure
     • Double bonds opens up to hold Hydorgen
   • Electrophillic Addition
     • Electrophiles - electron pair acceptors
       • Positively charged ions
       • Polar molecules

2. Alcohols and Other Organic Coumpouds

3. Hydrogen Bonding

   • Strongest intermolecular force
     • Higher melting and boiling points
       • More energy needed to overcome bonds
   • Only happens when H bonds to F,O,N
     • As they are very ELECTRONEGATIVE
   • Bond is so POLARISED + hydrogen has such a high charge density as it is so small
     • Hydrogen forms strong bonds with lone pairs on F,O,N
   • Examples
     • -OH
     • Ammonia + water
     • -NH
   • Ice is less dense than water
     • Ice - max no. of Hydrogen bonds
     • Lattice structure 'wastes' space
     • Ice melts - bonds break - lattice breaks down - molecules fill space
   • Causes some polymers to dissolve in water
     • Polym

4. Polymers

   • Addition Polymerisation
     • Double bond in alkenes opens up and joins with other alkenes to form a long chain
     • Poly(ethene) from ethene
   • Copolymers
     • Made from more than one type of monomer
     • Join together in a random order
   • Monomers
     • Always have double bonds
     • Poly(alkanes) - unreactive
   • Cross-linking
     • Thermoplastic polymers
       • no cross-linking
       • weak intermolecular forces
       • easy to melt
       • can be melted and remoulded as many times as you want
       • cools and hardens to form a shape
     • Thermosetting polymers
       • 3D giant covalent structures
       • don't soften when heated
       • strong
       • covalent cross-links
       • hard
       • rigid
       • insoluble
   • Uses
     • Poly(chloroethene) - flexible, durable, water pipes, insulation
     • Polystyrene - cheap, light, good insulator, crash helmets
     • Perspex - transparent, strong, used in place of glass
     • Poly(tetrafluoroethene) PTFE - chemically inert, non stick frying pans

5. E/Z Isomerism

   • Stereoisomerism
     • Def: Same structural formula but different arrangement in space
     • Single bond - atoms can rotate freely
     • Double bond - Atoms can't rotate or bend
       • Is rigid
   • Cis-Trans Isomers
     • Cis = E Isomers
     • Trans = Z Isomers
   • Each group linked to carbon has different priority
     • Br has a higher priority than F
     • CH3 has a higher priority than H
     • If two carbons have their higher priority groups on OPPOSITE sides, it is an E isomer
     • If two carbons have their higher priority groups on SAME sides, it is an Z isomer

6. Infrared Spectroscopy

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