2.1.3 Alkenes

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What are alkenes?
unsaturated hydrocarbons
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What does an alkene double bond consist of?
one sigma and one pi bond
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What is a pi bond?
an exposed area with a high electron density
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How does the pi bond form?
sideways overlap of 2 p-orbials on each C atom // forms pi bond above and below the plane
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describe the shape and structure of alkenes
trigonal planar // 120
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How do you form an alkane from an alkene?
hydrogenation// addition// ticket catalyst and hydrogen gas
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how do you form a dihalogenoalkane from an alkene?
electrophilic addition// halogenation // heterolytic fission
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what is an electrophile?
an electron pair donor
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describe the separation and recycling of waste polymers
sorted into different types of polymers // recycled by melting and remoddling
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How are waste polymers used as feedstock for cracking?
allows new production of plastics/ chemicals
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How are waste polymers used in energy production?
incinerated // heat produced used to generate electricity// combustion of halogenated alkenes can lead to toxic waste
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What is polyethene used for?
plastic bags, buckets, bottles // flexible easily moulded chemical proof low density
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what is polypropene used for?
utensils, containers, fibres // stiff
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what is a polymer?
long molecular chain built from monomer units
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why are polyalkenes unreactive?
strong C-H and C-C bonds
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what is the industrial importance of alkenes?
formation of useful polymers// manufacture of margarine
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how is margarine manufactured?
hydrogenation pf unsaturated veg oils using H and nickel catalyst // double bonds broken to lower BP
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What are the ways in which waste polymers are processed?
seperation and recycling // feedstock for cracking // combustion for energy production
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How is the environmental damage from waste polymers being minimised?
removal of toxic waste products post-combustion // development of biodegradable and compostable polymers from isoprene/ maze/ starch
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How do you test for unsaturation?
bromine dissolves in water to form orange solution // added to alkane it remains orange // added to alkene it goes colurless
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What happens if an unsymmetrical alkene undergoes halogenation?
can lead to formation of two isometric products
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Describe the production of alcohols
mainly done industrially due to high pressure // high atom economy as no waste products
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How are addition polymers made?
polymerisation of monomer to polymer
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Card 2

Front

What does an alkene double bond consist of?

Back

one sigma and one pi bond

Card 3

Front

What is a pi bond?

Back

Preview of the front of card 3

Card 4

Front

How does the pi bond form?

Back

Preview of the front of card 4

Card 5

Front

describe the shape and structure of alkenes

Back

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