Organic Flashcards
what is crude oil and where does it come from?
a finite resource that is found in the Earth’s crust. a mixture of hydrocarbons, mainly alkanes, formed over millions of years from the remains of ancient dead marine organisms.
describe the composition of crude oil
- The carbon atoms in these molecules are joined together in chains and rings
- each carbon atom is connected to 2 hydrogen atoms
what is the general formula for alkanes?
CnH2n+2, where n is the number of carbon atoms in the molecule
names of the first four alkanes
- methane
- ethane
- propane
- butane
process of fractional distillation in 4 steps
- heated crude oil enters a tall
fractionating column, which is hot at the bottom and gets cooler towards the top - vapours from the oil rise through the column
- vapours condense when they become cool enough
- liquids are led out of the column at different heights
state the names and uses of 5 fuels that are produced from crude oil by fractional distillation
- liquefied petroleum gases- fuel for domestic heating and cooking
- petrol- fuel for cars
- kerosene- fuel for aircrafts
- diesel- fuel for some cars and power stations
- bitumen- for roads and roofs
- (Lazy Penguins Keep Drinking Hot Beer.)
3 properties of hydrocarbons with 1-4 carbon atoms
gases fraction contains hydrocarbons with one to four carbon atoms
* boiling points below room temperature
* they are very
flammable
* have a low viscosity
3 properties of hydrocarbons with more carbon atoms
bitumen fraction contains hydrocarbons with more than 35 carbon atoms. These have:
* boiling points well above room temperature
* are very difficult to ignite
* have a high viscosity
what is the general equation for the complete combustion of hydrocarbon fuels?
hydrocarbon + oxygen → carbon dioxide + water
how to write a cracking equation
- The starting compound will always fit the rule for an alkane, CnH2n+2.
- The first product will also follow this rule.
- The second product will contain all the other C and H atoms.
- The second product is an alkene, so it will follow the rule CnH2n.
what happens in cracking?
The breaking down of large hydrocarbon molecules into smaller, more useful hydrocarbon molecules by vaporising them and passing them over a hot catalyst.
define saturated
A saturated hydrocarbon contains no carbon-to-carbon double bonds, only single bonds.
are alkenes and alkanes saturated or unsaturated?
alkanes are saturated, alkenes are unsaturated because unsaturated, because they contain a C=C double bond, which means that they have two fewer hydrogen atoms than the corresponding alkane
define unsaturated
An unsaturated compound contains at least one double or triple bond.
describe the test for alkenes
- Alkenes will react with bromine water and turn it from orange/brown to colourless. This is the way to test for a double C=C bond in a molecule.
- this is because as a result of being unsaturated, alkenes are more reactive than alkanes.
- Alkenes can take part in reactions that alkanes cannot.
- For example, ethene molecules can react together to form poly(ethene), a
polymer.
2 reasons cracking is important
- It helps to match the supply (how much of a fraction an oil refinery produces) of fractions with the demand for them since smaller hydrocarbons are more useful as
fuels
than larger hydrocarbons - It produces alkenes, which are useful as feedstock (A raw material used to provide reactants for an industrial reaction.) for the petrochemical industry.
first four alkenes
- ethene
- propene
- butene
- pentene
structure of ethene
- C2H4
- each C has 4 bonds as always
- but there is one C=C functional group (double bond)
H H
C = C
| |
H H
structure of propene
- C3H6
- each C has 4 bonds as always
- but there is one C=C functional group (double bond)
structure of butene
- C4H8
- each C has 4 bonds as always
- but there is one C=C functional group (double bond)
structure of pentene
- C5H10
- each C has 4 bonds as always
- but there is one C=C functional group (double bond)
what is a functional group
An atom, or group of atoms, that determines the main chemical properties/ typical reactions of an organic compound.