DJA 5). Alkenes
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general formula of alkenes
CnH2n
whats special about alkenes
c=c (carbon-carbon double bond) restricts rotation of groups attached (therefore E/Z isomers)
how many electrons does the c=c contain and what do we think of it as
4 electrons electron dense so has potential to attract d+ or positive ions so is reactive
electrophiles are
species looking for a pair of electrons (eg H+)
induced dipole of Br2 by c=c
electron dense c=c ‘pushes’ electron density in Br2 from one side to another causing a temporary dipole
structure of the carbocation
positively charged ion. when the reaction is occurring the Br can attach onto carbon 1,2,3…..
primary secondary and tertiary structures - how to identify
find the special bit (in our case the positive charge) find the carbon it is related to find how many carbons this carbon is attached to (1=primary, 2=secondary…)
primary secondary and tertiary structures - which is least stable
primary
primary secondary and tertiary structures - which is most stable
tertiary
electrophilic addition of H2SO4 to alkenes • type of reaction • what type of h2so4 is used • what can happen to the product
• very exothermic • conc h2so4 is used • product can be converted into alcohol by addition of water (H2SO4 is reformed so has acted as a catalyst
test for c=c
add orange Br2 water –> decolourises
polymer defintion
large molecule made up of lots of repeating units called monomers
how to modify plastics
add plasticisers they are small molecules that can get in between the chain of polymer, force them apart and allow them to slide over each other
poly(chloroethane) is also known as…
PVC
two types of poly(ethene)
LOPE HOPE
when do you get LOPE poly(ethene)
high pressure high temperature produces branch chain polymers which don't pack well molecules are flexible uses - plastic bags, electric cables
when do you get HOPE poly(ethene)
just over room temp and pressure less branching so more closely packed molecules are inflexible uses - crates, bottles, buckets
environmental issues with poly(ethene)
made from crude oil thereofre non-renewable inert as non-polar non biodegradable high melting point as strong vdw between molecules
alcohol functional group
O-H
two ways to produce ethanol
direct hydration fermentation
comparing direct hydration and fermentation - rate of reaction
DH vs fermentation fast vs slow
comparing direct hydration and fermentation - cost
DH vs fermentation expensive vs cheap
comparing direct hydration and fermentation - manpower
DH vs fermentation low vs high
comparing direct hydration and fermentation - purity
DH vs fermentation pure vs impure