BRAINCAKEAlkenes
Revision notes for Alkenes in AQA Chemistry (7404). 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.
- General FormulaAlkenes are a homologous series of hydrocarbons that contain at least one carbon to carbon double bond, C=C.
- Naming AlkenesAlkenes are named using IUPAC rules.
- BondingA C=C double bond is made of two different kinds of covalent bond: one sigma (σ) bond and one pi (π) bond.
- Position IsomerismStructural isomers have the same molecular formula but a different structural formula.
- Geometric IsomerismStereoisomers have the same structural formula but a different arrangement of their atoms in space.
- Nomenclature (Cahn-Ingold-Prelog)Cis/trans only works when there are identical groups to compare.
- Physical Properties of AlkenesAlkenes are almost non-polar: C and H have very similar electronegativities, and the C=C bond is between two identical atoms.
- CombustionAlkenes burn in oxygen.
- ElectrophilesAn electrophile is an electron pair acceptor.
- Electrophilic AdditionThe typical reaction of alkenes is electrophilic addition.
- Reaction with HalogensAlkenes react with halogens at room temperature by electrophilic addition.
- Reaction with Hydrogen HalidesAlkenes react with hydrogen halides (HCl, HBr, HI) at room temperature to form halogenoalkanes.
- Asymmetrical AlkenesAn asymmetrical (unsymmetrical) alkene has different groups on the two carbons of the C=C, such as propene, CH3CH=CH2.
- Reaction of Alkenes with HalogensThe addition of bromine to a C=C gives a simple test for unsaturation.
- Reaction with COncnetrated Sulfuric AcidAlkenes react with cold concentrated sulfuric acid by electrophilic addition.
- Asymmetrical AlkenesAsymmetrical alkenes react with concentrated sulfuric acid, and then water, to give a major and a minor alcohol.
- Reaction with WaterAlkenes react with steam to form alcohols.
- Addition PolymersAlkenes and substituted alkenes can join together in very large numbers to form addition polymers.
- Identifying the Repeating GroupAn addition polymer chain is built from one small section that repeats over and over: the repeating unit.
- Identifying the MonomerYou also need to work backwards: given a polymer or its repeating unit, find the monomer.
- Low and High Density PolythenePoly(ethene) can be made in two quite different forms by changing the reaction conditions.
- BiodegradabilityA material is biodegradable if it can be broken down by microorganisms, such as bacteria and fungi, into small molecules like carbon dioxide and…
- Solutions to Plastic PollutionBecause poly(alkenes) do not biodegrade, the way plastic waste is handled matters.