4.1.3 alkenes mindmap

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  • Created by: avocado05
  • Created on: 25-02-22 19:47
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  • alkenes
    • test for alkenes
      • shake alkene with orange bromine water
        • decolourises
          • Br adds across, forming di- bromoalkane
    • contains double bonds
      • causes restrictive rotation
        • contains pi bond
          • sideways overlap of adjacent p-orbitals above and below the bonding C atoms
        • contains sigma bond
          • overlap of orbitals directly between the bonding atoms)  
    • shape of alkenes
      • trigonal planar
      • bond angle of 120 degrees
        • the electron pairs repel each other equally
          • no lone pairs
      • aliphatic
        • unsaturated
    • stereoisomers
      • compounds with the same structural formula but with a different arrangement in space
        • E/Z isomerism
          • caused by restrictive rotation around double C bond
            • requires two different groups to be attached to each carbon atom of the C=C group
      • cis/trans isomerism
        • a form of E/Z isomerism
          • two of the substituent groups attached to each carbon atom of the C=C group are the same
    • reactivity
      • more reactive than alkanes
        • alkanes only contain sigma bonds
          • therefore have higher bond enthalpy
            • because they have a higher elec. density
        • alkanes are non-polar
          • requires more energy to react/break
        • alkenes contain sigma and pi bonds
          • pi bonds are weaker and have lower elec. density
            • lower bond enthalpy
          • likely to be attacked by electrophiles
            • electron pair acceptors
      • hydrogenation
        • Ni catalyst, 150C
      • hydration
        • H2PO4 catalyst, 300C, steam
          • heterolytic fission
    • markownikoff's rule
      • the major product from addition of a H halide to an unsymmetrical alkene
        • one where the hydrogen adds to the carbon with the most hydrogens alr attached
        • major product more likely to form
          • tertiary/secon-dary carbocation more stable than primary carbocation

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