O1: 14 Alkenes Flashcards
What are alkenes?
Unsaturated hydrocarbons.
What does bonding in alkenes involve?
A double covalent bond which is a centre of high electron density.
Name and outline the mechanism and conditions of the reaction between an alkene and Br2.
Electrophilic addition.
Aqueous Br2 (bromine water)
See sheet.
Name and outline the mechanism and conditions of the reaction between an alkene and HBr.
Electrophilic addition.
HBr.
See sheet.
Name and outline the mechanism and conditions of the reaction between an alkene and H2SO4.
Electrophilic addition.
Cold, concentrated H2SO4.
See sheet.
Name and outline the mechanism and conditions of the reaction between an alkene and H2O.
Electrophilic addition.
H2O with a strong acid.
See sheet.
How do you test for alkenes?
Add bromine water and it will go from orange to colourless.
Why are major and minor products made in addition reaction of unsymmetrical alkenes?
Tertiary carbocations are the most stable so they will most often be made. (They have 3 R groups attached to the carbocation.)
Secondary carbocations have 2 R groups attached to the carbocation.
Primary carbocations are the least stable. (They have 1 R group attached to the carbocation.)
What are addition polymers formed from?
Alkenes and substituted alkenes.
What is the repeating unit of addition polymers?
A monomer but with the double bond opened out.
How do you name an addition polymer?
Poly(alkene)
Why are addition polymers unreactive?
Polyalkenes are saturated and the main carbon chain of a polyalkene is also non-polar.
What are the intermolecular forces between addition polymers?
Van der Waals forces.
The longer and closer the polymer chain, the stronger the vdW forces.
Short, branched chains have weaker vdW forces between molecules.
What are the uses of poly(chloroethene)? How are its properties modified using a plasticiser?
PVC has long, closely packed polymer chains, making it hard but brittle at rtp.
Rigid PVC is used to make drainpipes and window frames.
Plasticisers make a polymer more flexible by getting between the polymer chains and pushing them apart. This reduces the strength of the vdW forces, making the polymer easy to bend.
Plasticised PVC is much more flexible than rigid PVC and is used to make electrical cable insulation, flooring tiles, and clothing.
