15-16 Flashcards
(29 cards)
how does infrared spectroscopy work
the IR radiation is absorbed by the covalent bonds in the molecules, increasing their vibrational energy
what is fingerprint
it’s the region between 500 and 1500cm-1
it’s unique to a particular compound
why are alkenes unsaturated
they make more bonds with extra atoms in addition reactions
what happens in electrophiles addition
the double bonds open up and atoms are added to the carbon atoms
they happen because the double bond has a lot of electrons and is easily attacked by electrophiles
what are electrophiles
they’re electron pair acceptors, they’re usually a bit short of electrons so they’re attracted to areas where a lot of them are
ex. electrophiles — H+ or NO2+
or polar molecules
what happens when hydrogen halides are added to unsymmetrical alkenes
they form two products
the amount depends on the carbocation
the more alkyl groups the more stable because alkyl groups feed electrons towards +ve charge
major product and minor product
what’s the least to most stable carbocations
primary is the least as it has one alkyl groups
secondary
tertiary is the most as it has 3 alkyl groups
what are the end products when cold concentrated sulphuric acid is mixed with propane. then cold water is added to the mixture and the mixture is warmed
when water is added and warmed it makes an alcohol and sulphuric acid
what are polymers
they’re long chain molecules formed when lots of monomers join together
what are two types of synthetic polymers
nylon and kevlar
what are properties of polyalkenes
they’re saturated
very in reactive
usually non polar as they’re only held by VDW forces
long straight chains are strong and rigid
brained short chains are weaker and more flexible
what do plasticisers do to polymers
adding plasticiser to a polymer makes it more flexible
they get between the polymer chains and push them apart reducing the strength of the IMF between chains so they’re attracted to slide around more
what happens to PVC when plasticiser is added and what are uses of plasticised PVC
when you add plasticiser PVC becomes more flexible because the plasticisers get between the polymer chains and push them apart reducing the strength of IMF between chains do they slide over each other more easily
uses
electrical cable insulation
flooring tiles
clothing
how does distillation help separate a liquid product from liquid by products
each liquid in the mixture has a different bp
collecting only the liquid fraction that boils at a particular temp will separate it from the mixture
how do u dehydrate alcohols
by eliminating water
ethanol is heated with a concentrated sulphuric acid catalyst
the product is usually a mixture with water acid and reactant in it so the alkene has to be separated out
basically how it works is that a lone pair of electrons from oxygen from the OH bonds to a H+ ion from the acid
what’s the benefit in dehydrating an alcohol
produce alkenes from renewable recorded
like ethanol from fermentation
you can produce polymers without needing oil
how do u hydrate an alkene
to produce alcohols
to hydrate the alkene by using steam in the presence of an acid catalyst
what pressure and temp do you need to turn ether to ethanol by steam
using a phosphoric acid catalyst
at 300 degrees
and 60atm
how do you ferment glucose
- fermentation is an exothermic process, carried out by yeast in anaerobic conditions
- yeast produces an enzyme which converts sugars, such as glucose into ethanol and co2
- the enzyme works at 30-40c
if too cold it will be slow if too hot it will denature - once formed ethanol is separated from the rest of the mixture by fractional distillation
- fermentation is low tech so it’s cheap equipment and renewable resources
the distillation is to purify the ethanol produced using this method takes extra time and money
what are adv and disadv of biofuels
- biofuels are renewable energy resources
won’t run out so they’re more sustainable - they produce CO2 when they’re burnt but it’s later absorbed by the plants while growing so they’re carbon neutral
disadv
petrol car engines would have to be modified to use fuels with high ethanol concentrations
when you use land used to grow crops for fuel that land can’t be used to grow food
so it takes a lot of space
what’s the chemical equations of bio ethanol being carbon neutral
6CO2 + 6H2O —> C6H12O6 + 6O2
C6H12O6 —> 2C2H5OH + 2CO2
2C2H5OH + 6O2 —> 4CO2 + 6H2O
how isn’t bioethanol fully carbon neutral
burning the fuel to power this machinery like transportation and refine and harvest produces CO2 sooo it isn’t fully carbon neutral
what are the conditions for industrial fermentation of glucose
in the presence of yeast
at temp of between 30-40
anaerobic conditions
how do oxidised alcohols
by adding the oxidising agent acidified potassium dichromate
it goes from orange to green
orange in alcohol and green when oxidised
