alkenes Flashcards
what is an alkene
unsaturated hydrocarbons with a C=C double bond
what is the general formula of an alkene
CnH2n
why no rotation about the C=C double bond
due to pi orbital - electron density above and below the single bond, which holds the carbon atoms in place
are alkenes more or less reactive than alkanes
more reactive, due to high electron density of double bond and the fact the pi-bond is slightly easier to break
what intermolecular forces of attraction do alkenes have
only van der waals due to non-polar bonds
are alkenes soluble in water
no
3 kinds of isomerism alkenes can have
chain isomers
position isomers
geometric E-Z isomers
what is an electrophile
electron deficient atoms/ions which accept a pair of electrons
what is the most stable kind of carbocation intermediate
alkyl groups have a positive inductive effect, so 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
what conditions are needed for the electrophilic addition of H2O to an alkene
acid catalyst, usually phosphoric acid
what are the products of the reaction
an alcohol
what conditions are needed for the electrophilic addition of a hydrogen halide to an alkene
room temperature
what conditions are needed for the electrophilic addition of a halogen molecule to an alkene
room temp and an organic solvent
how does a molecule with a non-polar bond react as if it is an electrophile
C=C double bond with a high electron density induces a temporary dipole in the halogen molecule –> delta positive atom attracted to double bond
how would you turn the product into an alcohol and how does 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 molecules
what are monomers and 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
give 3 uses of poly(cholorethene)
(PVC)
drainpipes
vinyl
aprons
give two 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 the physical properties of PVC change due to a plasticiser
PVC with plasticiser become flexible, used for aprons
without, it 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 biodegrabability in compounds with C-C or C-H bonds a problem
disposal is 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
what is a problem with recycling
each time thermosoftening plastics are melted and remoulded, their properties degrade, so they can only be remoulded a limited number of times
