Alkenes Flashcards
What is the general formula of an alkene
CnH2n
what kind of isomerism does an alkene form
E/Z
how is an alkene formed
Through cracking
what are the uses of alkenes
plastics, etc
how do we test for an alkene
bromine water
orange to colourless
what are the two types of polymers
-natural and synthetic
Why do EZ isomers form
because of restricted rotation
Why are alkenes unsaturated?
they have a double bond
why are alkenes reactive
double bonds have high electron density
What kind of reaction do alkenes undergo
electrophilic addition
What are electrophiles
Electron pair acceptor
Give examples of electrophiles
H-BR, H2SO4, BR-BR
How do we test for alkenes
add bromine water (example of electrophilic addition)
Positive test: orange to colourless
Why is Br-Br polarised
when bromine molecule approaches an a double bond, electrons shift to the other side, because they repel, this makes an induced dipole
How do we know what the major or minor product would be
- Depends on stability
- more alkyl groups bonded to carbocation the more stable the intermediate it
- alkyl groups push electrons towards positive carbocation making it more stable
What alkenes produce multiple products
Unsymmetrical
How can we make alcohol from alkyl hydrogen sulfates
add cold water to warm ethyl hydrogen sulfate will form ethanol
this is called hydrolysis
What are the two types of polymers
Natural: proteins and rubber
Synthetic: poly(propene)
Why can’t poly(alkenes) degrade
- Saturated molecules
- non polar which means they are unreactive
- which means it can’t be attacked by nucleophiles
What are the properties of polyalkanes
- Strong intermolecular forces for long chains, because
- This makes them rigid and stronger
Shorter polymers
- have less van der waals, and have branches
- flexible
- weaker
Polyalkanes with halogens
- form stronger perement dipole dipole
- so they last longer
What is the role of plasticers
- Make polymers more flexible
- they slide between the polymer chains pushing them apart, this weakens the van der waal forces between the chains, which makes them easier to slide over
- so this means the polymer is easier to bend
- PVC is used in pipes and stuff
