BRAINCAKEAlkenes
Revision notes for Alkenes in Edexcel Chemistry (8CH0). Read the start of any lesson here, then sign in free for the whole lesson, the R.E.C.I.P.E. recall steps and the quiz.
- AlkenesAlkenes are unsaturated hydrocarbons that contain at least one C=C double bond.
- Bonding in AlkenesThe C=C double bond in an alkene is made of two different kinds of covalent bond: one σ (sigma) bond and one π (pi) bond.
- Addition ReactionsAlkenes are unsaturated: they contain a C=C double bond, so more atoms can be added to the molecule.
- HydrogenationHydrogenation is the addition of hydrogen across a C=C double bond.
- HalogenationAlkenes react readily with the halogens chlorine and bromine at room temperature.
- HydrationHydration is the addition of water across a C=C double bond.
- Addition of Hydrogen HalidesAlkenes react with the hydrogen halides HCl, HBr and HI at room temperature.
- ElectrophileAn electrophile is an electron pair acceptor.
- NucleophileA nucleophile is an electron pair donor.
- Electrophilic Addition MechanismAlkenes react with electrophiles by electrophilic addition.
- Electrophilic Addition of Hydrogen HalidesHydrogen halides add to alkenes by the same electrophilic addition mechanism as bromine, with one difference in how the electrophile arises.
- Unsymmetrical MoleculesWhen a hydrogen halide adds to an unsymmetrical alkene, such as propene, the H can join either carbon of the C=C, so two different products are…
- Addition PolymerisationAddition polymerisation joins many small alkene molecules, called monomers, into one very long chain molecule, a polymer.
- Identifying the MonomerGiven a section of an addition polymer, or its repeat unit, you can work backwards to find the monomer.
- Identifying the Repeating GroupThe repeat unit is the smallest part of a polymer chain that repeats over and over to build the whole chain.
- Polymer WasteAddition polymers such as poly(ethene), poly(propene) and PVC are cheap, strong, light and long-lasting, so huge amounts are made.
- RecyclingRecycling reuses waste polymers instead of sending them to landfill.
- IncinerationIncineration means burning waste polymers at high temperature.
- Biodegradable PolymersA biodegradable polymer is one that can be broken down by microorganisms (bacteria and fungi) into simple substances such as carbon dioxide and water.