Flashcards in Organic Chemistry Deck (111)
What is crude oil
A mixture of hydrocarbons with a range of boiling points
How is crude oil formed
Crude oil was formed millions of years ago from the remains of dead sea creatures that fell to the seabed.
These remains were covered by mud and bacteria and then decayed slowly in the oxygen-free environment.
The deposits became buried under more sediments, and the underground pressure together with heat slowly converted organic matter into crude oil and natural gas.
What is fractional distillation
The use of distillation to separate a mixture of miscible liquids, making use of different boiling points
How does fractional distillation work
The fractioning column has a large surface area.
Evaporation followed by condensation of the vapour takes place many times on the surface of the fractioning column.
Only the vapour with the lowest boiling point reaches the top of the column and condenses to be collected as a liquid.
This continues until the fraction with the highest boiling point condenses.
What happens in the industrial process of fractional distillation
It occurs in a tall tower which is hottest at the bottom and gradually cools towards the top. The process is continuous.
This process pipes off the different fractions at different points in the same column.
Give the order of the fractions that come out of crude oil
Source for experiment, approx BP, number of carbons and use as fuel of refinery gases
Butane lighter, around 40 degrees, 1-4 carbons, domestic heating and cooking
Source for experiment, number of carbons and use as fuel of gasoline
Light petroleum, 4-12 carbons, petrol for motor vehicles
Source for experiment, number of carbons and use as fuel of kerosene
Paraffin, 9-16 carbons, jet aircraft fuel
Source for experiment, number of carbons and use as fuel of diesel oil
Petroleum, 15-25 carbons, diesel fuel for cars and lorries
Source for experiment, number of carbons and use as fuel of fuel oil
Central heating oil, 20-70 carbons, oil powered central heating systems
Source for experiment, approx BP, number of carbons and use as fuel of bitumen
Bitumen paint, around 400 degrees, more than 70 carbons, road making
What happens to the BP, volatility and viscosity as the number of carbon atoms in the molecule increases
Liquids become less volatile
Liquids become for viscous
Burn less easily
Why does BP increase as the number of carbon atoms in the molecule increases
Because there are larger intermolecular attractions between larger molecules so more energy is needed to separate the hydrocarbon molecules.
Why do liquids become less volatile as the number of carbon atoms in the molecule increases
Larger molecules evaporate more slowly because there are stronger intermolecular attractions
Why do liquids become more viscous as the number of carbon atoms in the molecule increases
Because of greater intermolecular attractions
What are the dangers of incomplete combustion
If a hydrocarbon is is burnt in a limited supply of oxygen, carbon monoxide is formed. This is toxic to humans because it reduces the capacity of the blood to carry oxygen.
What is photochemical smog and the dangers
In a car engine, the temperature is high enough that nitrogen and oxygen rom the air react to form nitrogen oxides. These react in the air with hydrocarbons to form photochemical smog. This can lead to poor air quality and respiratory diseases
What is acid rain and the dangers
If sulphur is present in fuels, sulphur dioxide may form when they are burnt.
This dissolves in water droplets in the atmosphere to form sulphuric acid.
This can cause damage to plants, animals and limestone buildings. Nitrogen oxides dissolve in water to form acid rain too
What are hydrocarbons
Molecules made up of hydrogen and carbon atoms only
What does organic mean
A compound containing at least one carbon-hydrogen bond
What is a homologous series
A family of compounds with similar properties due to their similar bonding. They have the same general formula
What does saturated mean
A compound consisting of single bonds ONLY
What does unsaturated mean
A compound containing a carbon-carbon double bond
What is the definition of "general formula"
A formula that describes a homologous series from which you can derive the molecular formula
What is the definition of the "molecular formula"
Formula that describes the number of each type of atom in a molecule
What is the definition of the "empirical formula"
The simplest whole number ratio of atoms
What are (structural) isomers
Molecules with the same molecular formula but different structural formula
What are isotopes
Atoms of an element with a different number of neutrons
What is an allotrope
Forms of an element that exist in the same state but have different properties because the atoms are arranged differently
What is the structural formula
Eg: butane CH3CH2CH2CH3
What is the displayed formula
When you draw it out
What are alkanes
What is the general formula for alkanes
What are the products of complete combustion with alkanes
Alkane + oxygen = carbon dioxide + water
Eg: CH4 + 202 = CO2 + 2H2O
Why does incomplete combustion occur
When there is not enough oxygen
What can the products of incomplete combustion be
CO + H2O
CO + C + H2O
C + H20
(C + CO + CO2 + H2O)?
Describe the halogenation of alkanes
Alkanes will react with a halogen with UV light present as an initiator of the reaction. It is a photochemical reaction.
A hydrogen atom in the alkane is replaced with a bromine atom - this is known as a substitution reaction.
What is the equation for the halogenation of methane with bromine
Methane + bromine = bromomethane + hydrogen bromide
CH4 + Br2 = UV = CBrH3 + HBr
What are alkenes
What is the general formula for alkenes
Why can't methene exist
Because there is only one carbon and the carbon cannot have a double bond with a hydrogen
Why does cracking take place
Because the demand for petrol is greater than the amount of gasoline fraction obtained from fractional distillation
Describe the process of cracking
Large, saturated hydrocarbons can be broken down into smaller hydrocarbons by a thermal decomposition reaction known as cracking. The reaction also produces small alkenes.
The reaction requires vigorous heating and an aluminium oxide catalyst.
What is the cracking reaction for decane
C10H22 = Al2O3, heat = C2H4 + C8H18
What does the reaction of cracking require?
Vigorous heating (about 600-700 degrees) and an aluminium oxide mixed with silicon dioxide. It can be carries out at higher temperatures without a catalyst.
What does a monomer have to have in addition polymerisation and why?
A double bond as it has to connect to the next monomer. There also needs to be heat, high pressures and an initiator. (NOT a catalyst as it gets used up in the reaction)
What is a monomer?
A molecule that can be bonded to other identical molecules to form a polymer.
What is a polymer?
Polymers are generally very big molecules with long chains of carbon atoms, they are made from smaller units called monomers.
Describe how ethanol can be made using ethene.
Ethanol can be made by the hydration of ethene (obtained from crude oil) with steam. The reaction is carried out at 300°C and 60-70 atmospheres pressure. A phosphoric acid catalyst is needed. It is a continuous flow process reaction. Only a small proportion of the ethene reacts first but the ethanol produced is condensed and the Unreacted ethene is recycled so the product produced is very pure and the yield is close to 100%.
Describe how ethanol can be made by the fermentation of sugar.
Yeast is added to a sugar or starch solution and left at 30-40°C for several days with no air. Enzymes in the yeast convert the sugar into ethanol and carbon dioxide. This happens as the sucrose reacts with water to form fructose and glucose which is then converted to ethanol and carbon dioxide. They require anaerobic conditions and get denatured if the temperature is too high. If the mixture contains more than 15% ethanol the yeast is killed so you can't make pure alcohol. It also takes several days and is a batch process. You can use fractional distillation to separate the water and ethanol but still maximum purity is 96%.
What are the two ways of making ethanol? Which is faster and which makes a more pure product?
Hydration of ethene and fermentation of sugar. Hydration of ethene is much faster as it is a continuous flow process not a batch process, and the product is pure. Fermentation can only contain about 15% alcohol.
Chemical equation for hydration of ethene:
C2H4 + H2O ---> CH3CH2OH
Chemical equation for fermentation of sugar:
C6H1206 ---> 2C2H5OH + 2CO2
Starting materials and where they come from for fermentation:
Sugar from sugar cane or sugar corn and yeast.
Starting materials and where they come from for hydration of ethene:
Ethene from crude oil and steam.
Positives of hydration of ethene
Continuous, quick process
Almost 100% pure ethanol produced
Good for countries with large crude oil reserves
What is dehydration of ethanol?
If the water is removed from ethanol, ethene is formed. This is called dehydration. It uses a hot aluminium oxide catalyst.
What is the equation for the dehydration of ethanol?
C2H5OH → C2H4 + H2O
How is an addition polymer formed?
By joining up many small molecules called monomers.
Is a monomer saturated or unsaturated? And a polymer?
A monomer is unsaturated and a polymer is saturated.
How do you test for alkenes?
Bromine water is an orange solution of bromine. It becomes colourless when shaken with an alkene. Alkenes can decolourise bromine water, while alkanes cannot.
what is substitution reaction?
In a substitution reaction, one atom is swapped with another atom.
When do alkanes undergo substitution reactions?
Alkanes undergo a substitution reaction with halogens in the presence of light.
What will happen to methane and bromine in the presence of UV light?
methane + bromine → methylbromine + hydrogen bromide
CH4 + Br2 → CH3Br + HBr
what happens when you add ethene to bromine water? give the symbol and word equation
ethene + bromine → dibromoethane
C2H4 + Br2 → C2H4Br2
Properties and uses of poly(ethene)
Light, stretchable polymer
Used to make packaging eg plastic bags, bottles and other containers
Why are addition polymers hard to dispose of?
They are inert due to the strength of the C-C bonds. This means that they are not biodegradable which causes problems with disposable. Burning plastics releases toxic gases.
What is condensation polymerisation?
Involves two different types of monomer that react together and bonds form between them, making polymer chains
For each new bond that forms, a small molecule (eg H2O) is lost
Why are alkenes much more reactive than alkenes
Because the double bond can allow another molecule to add on, so reactions of alkenes are known as addition reactions
What can the addition reaction of hydrogen to alkenes be used for?
Vegetable oils, which contain carbon-carbon double bonds are concerted to margarine by reaction with hydrogen.
Give an example of a condensation polymer
Explain what happens in condensation polymerisation
The water is lost so you cut out the H from one monomer and HO from the other monomer. So in the polymer between the blocks you delete the H2O. Double bond between carbon and oxygen. It happens at the end of each bond.
Properties and uses of poly(propene)
Strong, resistant to hear and chemicals, flexible
Used to make ropes, plastic crates, kettles and carpets
Properties and uses of poly(chloroethene)
Flexible, some rigidity, electrical insulator
Used to make clothes, drain pipes, electrical insulation
What happens in addition polymerisation
Small alkene molecules can react with themselves, usually when heated under pressure, to produce long chain molecules known as addition polymers.
The monomers polymerise to form one molecule of the polymer
How do you draw a polymer?
Flip the monomers double bond out outwards, draw a square brackets around it, and write an n in the bottom right outside of the bracket
Chemical equation for sucrose reacting with water to form glucose and fructose in fermentation
C12H22O11 + H2O = 2C6H12O6
Negatives of hydration of ethene
Uses finite resources
Needs high temperature and pressure so uses lots of energy
Describe the addition reaction of alkenes and hydrogen
Hydrogen adds to alkenes when they are heated together in the presence of a nickel catalyst, forming an alkane.
Describe the addition reaction of alkenes with aqueous bromine
Alkenes react with aqueous bromine to form colourless compounds, and this decolourising effect of an orange bromine solution is used as a test for alkenes because alkanes have no effect on aqueous bromine. (It is used to test for anything with a carbon-carbon double bond)
Part of the double bond breaks and the electrons are used to join two browmine atoms onto the carbon atom.. The product is 1,2-dibromoethane.
Positives of fermentation
Uses renewable resources
Good for countries that grow sugar beet or cane, Brazil has the climate
Little technology and low temperatures required
Negatives of fermentation
Can lead to the destruction of rainforests
Uses crops that would otherwise be used for food
Slow, batch process
Very impure, requires distillation, maximum purity 96%
What alkanes do you need to know?
Methane (MAIN COMPONENT IN NATURAL GAS)
What alkenes do you need to know?
What does biodegrade mean?
When a compound decomposes naturally or biologically due to bacteria or other organisms in the environment
What do you need to remember about drawing polymers?
Only one single carbon central bond, everything on the four branches, square brackets, little n
What do you need to remember about drawing monomers?
One double carbon central bond, everything on the four branches
What's the name of the isomer of bromomethane with two bromines.
(1,2) - dibromomethane
What is the name of butene with the structural formula
but-1-ene or butene
What is the name of butene with the structural formula
How do you name isomers? (if you know then dw, this is just clearly explaining for me)
The type of alkane or alkene (depending on if there is a double bond or not) depends on the longest chain
The numbers at the start depends on which branch the side chain is on - if there are two side chains, you write the numbers of both of the chains, even if they are on the same chain, write it twice (e.g. 2,2)
If the side chain is CH3 - methyl
If the side chain is CH3CH2 - ethyl
If there are two side chains sam]y "di" (e.g. dimethyl..)
Also with alkenes if, with alkenes, the double bond starts on the first carbon it is bun-1-ene for example, if it is on the second carbon it is but-2-ene and so on.
Structural formula of propene
CH3CH=CH2 (The = shows the double bond)
What is the trend in boiling points of the first eight alkanes and alkenes?
The boiling points goes up. They are all gases at room temperature up to pentane when the boiling point is above room temperature so they are liquids.
What happens when you mix methane and bromine gas and then expose it to light what changes and what is the equation for the reaction?
when you mix methane and bromine gas it is brown because of the presence of methane. When it is exposed to UV light it loses its colour as a hydrogen atom is substituted by a bromine atom. The mixture becomes bromomethane and hydrogen bromide gas is formed.
What happens when you burn alkanes?
you get carbon dioxide and water
What is the chemical equation for the substitution reaction between methane and bromine gas?
CH4(g) + Br2(g) ---> CH3Br(g) + HBr(g)
How can you test for an alkene?
If you shake an unknown organic compound with bromine water and the orange bromine water is decolorised, the compound contains a carbon-carbon double bond. If the unknown compound is a gas, simply bubble it through the bromine water and it will have the same effect.
What are alcohols?
Members of a large homologous series of similar compounds. Alcohols all contain an -OH group covalently bonded onto a carbon chain.
What pressure should the hydration of ethene be done at?
What is the BP of ethanol?
What temperature should the hydration of ethene be done at?
What is the catalyst for the hydration of ethene?
What happens if you burn ethanol?
What is the chemical equation?
All alcohols burn to form carbon dioxide and water
C2H5OH(l) + 3O2 ---> 2CO2(g) + 3H2O(l)
What is a biofuel?
A fuel made from biological sources, such as sugar cane or maize. Ethanol is a biofuel.
What is dehydration?
The removal of water from a compound
What is meant by the term volatile?
evaporates more easily
Why might oil companies want to crack a hydrocarbon?
it can produce ethene and propene which are useful molecules for the production of polymers. Also components of gasoline can be made.
Uses of nylon
textiles, fibres used in ropes and it can be cast into solid shapes for cogs and bearings in machines.
What monomers are used to make nylon?
a 6 carbon organic acid called a hexanedioic acid with a -COOH group at each end which is known as a carboxylic acid group.
The other monomer is a diamine called 1,6-diaminohexane with -NH2 at each end.