CH14 Alkenes Flashcards
What is an alkene
Unsaturated hydrocarbons with a C=C double bond
What is an alkene
Unsaturated hydrocarbons with a C=C double bond
General formula
CnH2n
Why is there no rotation about the C=C
Due to the pi orbital - electron density above and below the single bond holding C atoms in place
Are they more or less reactive than alkanes - why
More reactive - high electron density of double bond and pi-bond is slightly easier to break
What intermolecular forces of attraction do they have
Only van der Waals due to non-polar bonds
Are they soluble in water - why
Non, non-polar bonds
Name and describe 3 kinds of isomerism
Chain isomers (branched chains) Position isomers (C=C on different C atoms) Geometric E-Z isomers (Z - 2 highest atomic number chains are on the same side. E - they are on opposite sides)
What is an electrophile
Electron deficient atoms/ions which accept a pair of electrons
Most stable kind of carbocation intermediate - why
Alkyl groups have a positive inductive effect - the most stable carbocation is the one bonded to the most other carbon atoms
Major products will be formed from which kinds of carbocations
Tertiary (most stable available)
Conditions needed for the electrophilic addition of H2O to an alkene
Acid catalyst (phosphoric acid)
Products for this reaction
Alcohol
Conditions needed for the electrophilic addition of a hydrogen halide to an alkene
Room temperature
Conditions needed for the electrophilic addition of a halogen molecule to an alkane
Room temperature and organic solvent
How does a molecule with a non-polar bond react as if it is an electrophile
C=C with a high electron density induces a temporary dipole on the halogen molecule
How would you turn sulfuric acid and ethene into an alcohol - how does this show that sulfuric acid catalyses the addition of water to an alkene
Add water
H2SO4 reforms, showing it catalyses the hydration of alkenes
What is an addition polymer
Many monomers bonded together via rearrangement of bonds without the loss of any atom or molecule
What are monomers - what form do they usually take
Molecules which combine to form a polymer
Usually have a C=C bond which breaks to leave a repeating pattern
3 uses of poly(chloroethene)/PVC
Drainpipes
Vinyl
Aprons
2 examples of plasticisers
esters
phthalates
What are plasticisers
Small molecules that get between polymer chains to force them apart and allow them to slide over one another
How do physical properties of PVC change due to a plasticisers
PVC with a plasticiser becomes flexible, used for aprons
Without a plasticiser, PVC is rigid and used for drainpipes
Why do things containing mainly C-C and C-H bonds not decompose easily
Bonds are non-polar so are not attacked by enzymes
Why is a lack of biodegradability a problem
Disposal is very problematic
What is mechanical recycling
Where plastics are separated into different types, washed, ground down, melted and re-moulded
What is mechanical recycling used for
Soft drinks bottles –> fleeces
What is feedstock recycling
Plastics heated to a temperature which break polymer bonds, leaving original monomers that can be made into new plastics
What is feedstock recycling used for
Making totally new plastics
