4.1.3

    Cards (51)

    • Alkene general formula : Cn H2n
    • Alkenes are unsaturated
    • Bond angle around a Alkene double bond is 120 (planar)
    • In Alkenes carbons form sp2 and one 2p orbital
    • The 2p orbital on each carbon in an alkene double bond overlaps sideways to form a pi bond
    • The remaining 2p orbital of an alkene in a double carbon bond overlaps with the other directly between the bonding atoms forming a pi bond
    • Double carbon bonds are stronger than single carbon bonds
    • Double carbon bonds are formed from a pi and sigma bond
    • Sigma bonds are stronger than pi bonds
    • An Alkene double bond is an area of high electron density and negativity that attracts electrophiles
    • Electrophiles : an electron pair acceptor
    • Adding hydrogen is called hydrogenation
    • reactions involving electrophiles joining are called electrophilic addition mechanisms
    • Mechanisms contain: partial charges, lone pairs, ionic charge, curly arrows
    • Carbocation: positive carbon ion
    • cyclohexane + bromine water -> orange and yellow layers
    • cyclohexene + bromine water -> clear and white precipitate, presence of carbon double bond
    • markownikoffs rule
      A) major
      B) minor
    • monomers: small molecules, a single unit
    • polymers: multiple monomers joined together in repeating units
    • repeating units: small structures/ arrangements occurring over and over again
    • addition polymerisation flowchart: crude oil -> fractional distillation -> cracking -> polymerisation
    • during polymerisation the pi bond in the double carbon bond is broken and a new sigma bond is formed
    • a polymer is surrounded by brackets and has a small n to represent the number of repeating monomers
    • monomer -> polymer:
      A) =
      B) -
    • for complex polymers draw the repeating unit and condense the rest of the carbon chain
    • landfill: the disposal of waste material by burying it in a lined pit until it is full and recovered.
      x - plastics cannot break down due to lack of light water and oxygen
    • combustion: burning plastics
      + - release energy to generate electricity
      x - releases co2 and acidic gases ( the can be counteracted by base gas scrubbers)
    • reusing and recycling: using again or making something new
      + - carry out a function many times
      x - plastic must be sorted, expensive, concerns about quality and contamination
    • organic feedstock: polymers are broken into small organic molecules to be used in industrial reactions, a type of recycling
    • biodegradable polymers: break down via organisms and environmental conditions. contain plant starch and addition polymers
      x - addition polymers still released into the environment
    • bioplastic: a polymer made from renewable sources, can be considered carbon neutral if sustainable farming methods are used, fully biodegradable
    • photodegradable polymers: break down using energy wavelengths similar to light, affects bonds directly or an additive, cannot be stopped once it starts. must have sufficient light exposure ( that landfills don't have)
    • pi bond formation
      A) sideways overlap
      B) p orbitals
      C) pi bond
    • toxic gas HCl is neutralised by being passed through an alkali or carbonate
    • a carbon ring causes a hydrocarbon to loose 2 hydrogen atoms
    • reactivity of alkenes
      the pi bond is weaker than the sigma bond so is much easier to break so is more reactive
    • alkene + hydrogen
      requires nickel catalyst and 150c, forms alkane
    • alkene + halogen
      requires RTP, forms dihaloalkane
    • alkene + steam
      requires phosphoric (V) acid catalyst, 300c and 65 atm , produces alcohol
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