ORGANIC CHEM-pg 149 + how to draw Flashcards
what is a hydrocarbon
general formula for alkanes
what is a homologous series
compound formed from only H and C atoms
CnH2n+2
a group of organic compounds that react in a similar way and all have the same functional group
what are alkanes, explain why
.
what is a functional group
saturated hydrocarbons/compounds
each carbon atom has 4 single covalent bonds
part of molecule that determines how it will react
first 4 alkanes and their formulas
what is a displayed formula
methane CH₄
ethane C₂H₆
propane C₃H₈
butane C₄H₁₀
a drawing showing all atoms and bonds in molecule
what happens as length of carbon chain (hydrocarbon) gets bigger
the properties of a hydrocarbon affects …….
-viscosity increases (more gloopy, less runny)
-boiling point increases, volatility decreases- higher temp needed to vaporise/condense
-flammability decreases, harder to ignite
how the hydrocarbon is used as a fuel
equation for complete combustion of hydrocarbon fuels
what are the waste products
what is released
-Hydrocarbon + oxygen—> Carbon dioxide + water (and energy)
-Carbon dioxide + water (vapour)
-energy
explain what happens in combustion of Hydrocarbons
why are hydrocarbons used as fuels
the carbon and hydrogen in the fuels are oxidised (gain O₂)
bcse of amount of energy released in complete combustion
what is crude oil x3
-finite recourse in rocks (fossil fuel)
-Formed from remains of an ancient biomass, mainly plankton, that was buried in mud- under high pressure and time, became crude oil
-Mixture of many different compounds, mostly hydrocarbons, mostly alkanes
fossil fuels- coal, oil, gas are all…..
explain why
non renewable- finite recources
Used at faster rate than being formed
-What does fractional distillation do
-Explain how fractional distillation works 4 points
separate hydrocarbons in crude oil into fractions (w/ similar no. of carbon atom)
-Vaporise oil till it turns to gas- gases enter fractionating column
-in column, there is a temp gradient, Hot —> Cool
-longer hydrocarbons = higher boiling points. Condense into liquid + drain out early- near bottom.
Shorter hydrocarbons = lower b.p. Condense + drain out later, near top
-eventually Crude oil mixture separated into fractions w/ similar carbon atom no. so similar bp’s
5 gases u know that are produced from crude oil- rely on in life
From highest to lowest boiling point
.
what is lpg made of
heavy fuel oil-ships
diesel oil-trucks/buses
kerosene-plains
petrol-cars
Liquified Petroleum Gas-camping stoves, heating oil, lubricating oil
-mostly propane and butane
what happens to very short chain hydrocarbons in the fractional column
have really low boiling points
.all throughout the column, the temperature is hot enough to keep these as gas
they cannot condense - taken out from the top still in gas form
the fractions can be processed to produce…….
fuels and feedstock for the petrochemicals industry
what does feedstock mean
the petrochemical industry uses fractions of crude oil as feedstock to make new compounds for use in things like…. x4
a chemical used to make other chemicals
-polymers
-solvents
-lubricants
-detergents
The products of crude oil are all types of…..
The vast array of natural and synthetic carbon compounds is bcse of…
organic compounds (compounds containing carbon)
Carbon atoms ability to form families of similar compounds- different homologous series.
what is cracking
why is it done x2
What are the potential products of cracking x2
2 types of cracking
breaking down hydrocarbons into smaller, more useful molecules
Short chain hydrocarbons= more flammable=good fuels
Fuels w/ small molecules are in high demand
-alkanes, alkenes
-catalytic/ steam
what are alkenes used to produce x2-
some products of cracking are useful as
-Polymers. Starting material for producing other chemicals
-fuels
what type of reaction is cracking
Describe catalytic cracking -3 steps
Describe steam cracking- 3 steps
Thermal decomposition-break down molecules by heating
.
Both MUST be done under high temp (320* +)
.
-vaporise long chain hydrocarbon - heat to gas
-pass vapour over HOT powdered aluminium oxide catalyst
-long chain molecules split apart
-vaporise hydrocarbons
-mix them w/ steam
-heat to VERY high temp
C₅H₁₂ can be cracked into ethene and 1 other hydrocarbon,
Give balanced symbol equation for this
C₅H₁₂ —-> C₂H₄ + C₃H₈
why are alkanes useful as fuels
what are alkenes
they release energy when burnt
hydrocarbonsthat have functional group C=C
general formula for alkenes
why are alkenes unsaturated
why are alkenes more reactive than alkanes
first 4 alkenes
CnH2n
have C=C double bond so have 2 fewer hydrogens than an alkane w/ same carbon number
the C=C double can open up to make a single bond, the two C atoms can bind w/ other atoms
ethene
propene
butene
pentene
Akene+ Oxygen=
when alkenes are burnt in air, alkenes undergo….
standard equation for incomplete combustion of alkenes
what can be seen when alkenes incompletely combust
Carbon Dioxide + Water
incomplete combustion
Carbon+Carbon Monoxide+carbon dioxide +water (+energy)
smoky flame (yellow)
what are the cons of incomplete combustion of alkenes x2
Why are alkenes a homologous series
carbon monoxide is poisonous
releases less energy than complete combustion
all have the same functional group
what is a functional group
why do alkenes react similarly
alkenes usually react by what type of reaction-explain
group of atoms in a molecule that determine how a molecule reacts.
they all have C=C double bond
addition reactions. the c=c double bond opens to leave a single bond- new atom added to each carbon
what is hydrogenation of an alkene
what is the product
what is needed for hydrogenation
addition of hydrogen
a saturated alkane
a nickel catalyst
High temp (150* c)
alkene+ halogen=
ethene + bromine=
in general what is the reaction of an alkene and halogen like-
dihaloalkane (Di because there are 2 halogen atoms)
dibromoethane
-quite rapid- no special conditions needed
what happens when bromine water is added to a saturated compound
What happens when an bromine water added to alkene- unsaturated
the orange bromine water stays orange, no reaction
(the bromine will add across the double bond) decolourises bromine water- colourless dihbromo compound is made
alkene + water (steam) =
How do you do this
what conditions are needed-
how is ethanol made industrially x4
alcohol
mix alkene w/ steam and pass over catalyst
-high temp(300*) and 70 atm and phosphoric acid catalyst
.
–mix ethene w/ steam. Pass over a catalyst. put mixture into condenser.
ethanol + water have higher bp than ethene, condense.
unreacted ethene recycled back into reactor.
ethanol purified from mixture by fractional distillation
what are polymers
What happens in addition polymerisation
‘
What conditions are needed for it
in addition polymerisation, the monomer will always be a ….
example of monomers
long chains of repeating units- monomers
Many small molecules- monomers join to form large molecule-polymer.
high pressure, a catalyst
alkene
- poly(ethene) or poly(propene) through addition polymerisation
what are plastics made of
carbon based polymers, monomers are often alkenes
what happens in addition polymerisation
the monomers originally have double c=c bond.
these unsaturated monomers (alkenes) open up the double bond and join together to form polymer chains
in addition polymers, why does the repeating unit have the same atoms as the monomer
How can you tell which is the monomer and which is the polymer
bcse no other molecule is formed
(the polymer is the only product)
monomer has C=C double bond
polymer has c-c bond
the monomers a polymer is made from affects the…… of the …… As there are many ………. there are many different ……
the monomers a polymer is made from affects the properties of a plastic. As there are many monomers there are many different plastics
How to draw displayed formula from of addition polymer from displayed formula of monomer - 4 steps
-how to go the other way round
how do you name a polymer
-draw the 2 alkene carbons, replace the C=C double bond with C-C bond
-add an extra empty bond to the side of each carbon
-fill in rest of bonds the way they are in the monomer.
-put brackets around the repeating bit- put n AFTER the brackets
—Draw out the repeating bi of the polymer
replace the C-C with C=C and get rid of the empty extra bonds
-poly(monomer) so if monomer is propene—- Poly(propene)