Alkenes

Structure

• Unsaturated hydrocarbons

• 2 covalent bonds between C=C atoms, centre of high electron density

Geometric Isomerism

• No rotation around C=C bond

• Priority group is the one with the highest mass number

• Priority group on same side = Z

• Priority group on different side = E

Forming low density polymers (poly(ethene))

• 200 degrees C

• 2000 atm

• In presence of O2

Properties of low density polymers

• Flexible and soft

• Molecules loosely packed due to branching

• Used to make bangs, cling film

Forming high density polymers (poly(ethene))

• 60 degrees C

• 2atm

• Ziegla-Natta catalyst

Properties of high density polymers

• Stiffer and harder than low density polymers

• Used to make buckets and bottles

Polymers and biodegradability

• Not biodegradable

• Because the long chains of C-C are non-polar

• and C-H are also non-polar

• Addition polymers are very unreactive

Polymer

Long chain molecule made from lots of small molecules joined together

Addition Polymerisation

Formation of long chain molecules from lots of small molecules joining together with no other products

PVC

• Poly(chloroethene)

• Addition polymer with waterproof properties

• Gains these properties by addition of plasticisers during the reaction

Electrophilic Addition

C2H4 + Br2

• As Br-Br gets closer to the C=C

• The electrons will repel each other

• Creating an electronegativity in the Br-Br

Electrophilic addition and H2SO4

• H2SO4 → Makes alkye hydrogensulphate → Can be hydrolysed to produce ethanol