C7 (organic chemistry) Flashcards
how is crude oil formed?
- found in rocks - it’s a finite resource (will run out some day).
- 300-400 million years ago, organisms (such as plankton) died, sank to seabed. sediment fell on top of them. sediment and the water on top of them created high pressures and temperature, preventing them decomposing. chemically changed organic biomass into crude oil, and this soaked into the rocks, stored for millions of years
- we can extract this by drilling into the rock and sucking it up to the surface
how is crude oil a finite resource?
takes so long to form, so if we continue extracting it at the rate we are now, we’ll run out of it completely
- this is why we refer to fossil fuels (e.g. coal, oil, gas) as non-renewable
what is organic chemistry?
- involves molecules containing carbon
- carbon is useful as it forms 4 strong bonds with other atoms
what is a hydrocarbon?
a compound of carbon and hydrogen only. (e.g. crude oil is made up of a mix of different hydrocarbons. the temperature and pressure the solution is exposed to determines the types of hydrocarbons in the mixture).
what are the four types of alkanes and their formulas?
- methane (CH4)
- ethane (C2H6)
- propane (C3H8)
- butane (C4H10)
what is the rule for finding the formula for alkanes?
However many carbon atoms there are, double it and add two to find the number of hydrogen atoms.
what is an alkane?
scientists say that alkanes are saturated molecules. this is because the carbon atoms are fully covalently bonded to the hydrogen atoms.
why is the process of fractional distillation important?
- crude oil is made up of many hydrocarbons (mainly alkanes( with different boiling points (mixture of many different compounds)
- we must separate them in order for the hydrocarbons in the oil to be useful, and we do this through fractional distillation.
- in fractional distillation, crude oil is separated into fractions - these contain hydrocarbons with a similar number of carbon atoms.
describe the process of fractional distillation:
- takes place in large columns in oil refineries.
- the crude oil is heated to a very high temperature, causing it to boil.
- all the hydrocarbons evaporate and turn into a gas, which is then fed into the bottom of a fractional distillation column (above).
- the column is hotter at the bottom and cooler at the top.
- the hydrocarbon vapours now rise up the column, as hot air rises
- the different hydrocarbons condense (turn into liquid) at different points up the fractionating column, when they reach a region at a lower temperature than their boiling point the liquid fractions are then removed.
- very long chain hydrocarbons have very high boiling points, and so are all removed at the bottom of the fractionating column (e.g. bitumen, road surfacing, heavy fuel oil - heating oil, fuel oil, lubricating oil)
- very short chain hydrocarbons have very low boiling points, and do do not condense. these are removed at the top of the fractionating column as gases. (e.g. liquified petroleum gas, containing propane and butane)
describe fractions and their uses:
fractions contain hydrocarbons with a similar number of carbon atoms.
- petrol and diesel fuels cars.
- kerosene is used as jet fuel.
- heavy fuel oil is used to power ships.
- liquified petroleum gas is used in camping stoves.
- some fractions are used as feedstock (chemical used to make other chemicals) for the petrochemical industry.
- solvents
- lubricants
- detergents
- polymers
how does hydrocarbon chain length affect viscosity?
viscosity = the thickness of a fluid.
- fluids with a high viscosity flow slowly, e.g. honey.
- as the hydrocarbon molecule size increases, the molecules get more viscous. very long chain hydrocarbons flow very slowly.
- this is because it takes more energy for longer chain lengths to flow over itself.
how does hydrocarbon chain length affect flammability?
flammability = how easy hydrocarbons combust.
- short chain hydrocarbons are very flammable - methane is the gas used in bunsen burners.
- as the size of hydrocarbon molecules increases, the molecules become less flammable.
- this is because it’s less able to evaporate and convert into gas form.
how does hydrocarbon chain length affect the boiling point?
boiling point = temperature at which a liquid turns into a gas.
- short chain hydrocarbons have low boiling points.
- as chain length increases, the number of intermolecular forces increases - more energy is needed to separate longer molecules, meaning they have higher boiling and melting points.
- the first 4 alkanes are gases at room temperature. others are liquid or even solid at room temp
how does hydrocarbon chain length affect volatility?
volatile = the ability for a substance to evaporate
- short chain hydrocarbons are more volatile, due to their low boiling points
what are the two main features of alkanes?
- general formula of Cn (H2n+2)
- only have single covalent bonds between carbon atoms.
what is the disadvantage of using long-chain hydrocarbons as fuels, and what is the solution?
- not very flammable, don’t make good fuels.
- short chain hydrocarbons are flammable, and release lots of energy when burned with oxygen. under high demand - finite resource.
- must convert long-chain hydrocarbons into shorter-chain hydrocarbons.
- this process is called cracking.
what is cracking?
- thermal decomposition reaction. (uses heat to break down molecules)
long chain hydrocarbon broken down to produce smaller, more useful molecules. - this makes one shorter chain alkane (used for fuels in cars).
- also makes an alkene molecule.
what is the key point about the cracking equation?
longer chain alkane = shorter chain alkane + alkene
- number of carbons and hydrogens on each side must be the same
what are the required conditions for cracking?
- catalytic cracking: high temperature and catalyst (speeds up reaction).
- heat long chain hydrocarbons, vaporise them.
- use hot powdered aluminium oxide as the catalyst, and pass the vaporised hydrocarbon over it.
- as the long hydrocarbons come into contact with the catalyst, they split apart.
- steam cracking: high temperature and steam.
- heat long chain hydrocarbons, vaporise them.
- mix the vaporised hydrocarbons with steam, and heat them to a very high temperature.
- this causes the long hydrocarbons to split apart.
describe alkenes:
- (e.g. ethene) has double covalent bond between two carbon atoms. this makes them unsaturated - alkanes only have single bonds, making them saturated.
- very useful. used by adding them together to make polymers. the double bond can break to form two or more bonds to connect the adjacent atoms.
- used as starting material for other useful chemicals.
- more reactive than alkanes - has a double bond which can easily split open.
are alkenes saturated or unsaturated, and why is this important?
- unsaturated, as not all of the bonds are with hydrogen atoms - contains a double bond
- more reactive
- can form polymers, as the double bond can break to form 2 more bonds with adjacent molecules
what are the four alkenes and their formulas?
- methene (CH2)
- ethene (C2H4)
- propene (C3H6)
- butene (C4H8)
how do you test for alkenes?
- uses bromine water, which is orange.
- if you shake an alkene solution with bromine water, the bromine water will turn from orange to colourless.
- the bromine molecules replace the double bond in the alkene molecule. there is now no bromine molecule to keep the orange colour of the solution - this won’t happen with alkanes, as there is no double bond to break.
why do you get one alkane and one alkene when you split long chain hydrocarbons?
- take decane, which splits to make heptane and propene.
- as decane is ten carbons long, it splits to make heptane (7 carbons) and propene (3 carbons).
- if you did the same for hydrogens, there aren’t enough hydrogens left for both products to be saturated and have all single bonds.
- therefore, one of the products has to have a double bond, making it an alkene, rather than an alkane.
what is a homologous series?
a group of similar compounds with similar properties.
- alkanes and alkenes are both homologous series.
what is the alkene formula?
Cn H2n
the number of hydrogen atoms is double the number of carbon atoms.
what is the functional group of alkenes?
the carbon-carbon double bond is the alkene’s functional group, as its responsible for the alkene’s typical reactions.
what are addition reactions?
the double bond in the alkene opens up, so the two carbon atoms are able to bond to two atoms of another molecule, therefore ‘adding’ to the alkene. hence the name, addition reaction.
what are the products of complete and incomplete combustion?
complete combustion:
alkane/alkene + oxygen = water + carbon dioxide
incomplete combustion:
alkane/alkene + oxygen (limited/insufficient) = carbon monoxide + carbon (soot)
describe the addition reaction of alkenes with hydrogen (hydrogenation):
- take propene (three carbon chain).
- adding hydrogen to propene and supplying a catalyst will cause the double bond in the alkene to break apart, and the hydrogen atoms will then be able to bond to those carbon atoms.
- the product is propane, and it doesn’t have a double bond anymore. it’s now saturated. now an alkane
describe the addition reaction of alkenes with water (hydration):
- take ethene, and add water to it. react it with a catalyst and high temperatures.
- the water will actually be in the form of water vapour/steam due to the high temps
- the double bond on the alkene opens up, and the water molecule will split into a hydrogen atom and an O-H group. these can then bond with the vacant carbon atoms.
- the product is ethanol (an alcohol), as it as the O-H functional group
how do you separate ethanol from unreacted ethene and water after hydration?
- ethanol is used in many industrial processes, and is used to create alcoholic drinks.
- as ethene has a relatively low boiling point, cool the molecule, so the ethanol and water will condense into liquid form, while the ethene will remain a gas.
- to separate the water and ethanol, you must use fractional distillation.
- heat the mixture, the ethanol will boil first (lower boiling point), and will evaporate up through the fractionating column and then condense into a separate beaker.
describe the addition reaction of alkenes with halogens (halogenation):
- use ethene as an example.
- doesn’t require a catalyst
- take ethene, add it to bromine, and give it a shake. this will react to form dibromoethane.
- as this uses up all of the bromine, the orange colour disappears.
- the main test we use to distinguish alkenes from alkanes.
describe alcohols:
- homologous series
- look almost the same as alkanes, but has O-H functional group, in the place of one of the hydrogens.
what are the four types of alcohol and their formulas?
- methanol (CH3OH)
- ethanol (C2H5OH)
- propanol (C3H7OH)
- butanol (C4H9OH)
- always put OH at the end
- these first 4 have pretty similar properties
what is the general formula for alcohols?
Cn (H2n+1) OH
what are the properties of alcohols?
- flammability. can undergo complete combustion in air (makes a blue flame). react with oxygen to form carbon dioxide and water.
- solubility. can dissolve in water to form a solution. alcohols aren’t acidic or alkaline, so the solution will have a neutral pH.
- oxidisation. taking an alcohol and adding oxygen can form a carboxylic acid, which has the functional group of ‘COOH’.
what are the uses of alcohols?
- fuels (bio-fuels) as they’re flammable (releases lots of energy)
- solvents in industry. often used instead of water, as it can dissolve things that water can’t. e.g. hydrocarbons, lipid compounds (fats, oils).
- food and drink (ethanol only)
- sanitiser
- anti-septic
what are the 3 main uses of ethanol?
- chemical feedstock to produce other organic compounds
- biofuel (can be burned like petrol)
- alcoholic drinks (e.g. beer, wine, spirits)
how is ethanol produced through an addition reaction?
- can be produced commercially by reacting ethene with steam
- addition reaction as the water molecule is being added to the ethene molecule
- requires high temperatures and pressures, and a phosphoric acid catalyst
what are the advantages and disadvantages of producing ethanol through addition reactions?
advantages: ethene is cheap, the reaction itself is cheap and efficient
disadvantages: ethene is from a crude oil which is a non-renewable resource, so if it starts to run out it will become expensive
describe the production of ethanol through fermentation:
- fermentation is the anaerobic respiration of sugars by yeast cells to produce ethanol and carbon dioxide
- it’s anaerobic respiration (no oxygen)
- carried out in fermentation tanks. requires yeast cells which have naturally occurring enzymes to catalyse the reaction. temperatures of 30-40 degrees celsius (optimum enzyme temperatures). must be anaerobic conditions, so that ethanol isn’t oxidised to ethanoic acid
what are the advantages and disadvantages of the production of ethanol through fermentation?
advantages: the sugar/glucose is a renewable resource so can’t run out. yeast is easy to grow
disadvantages: the process can be relatively slow. the produced ethanol isn’t pure so must be separated through fractional distillation (energy consuming)
what are the four carboxylic acids and their formulas?
- methanoic acid (HCOOH)
- ethanoic acid (CH3COOH)
- propanoic acid (C2H5COOH)
- butanoic acid (C3H7COOH)
- COOH is the functional group of carboxylic acids.
describe carboxylic acids:
- a homologous series
- functional group COOH
- weak acids (only partially ionise). they
don’t lose all their hydrogen atoms. - low concentration of H+ ions. pH of 4-6.
how do we show the ionisation reaction of a carboxylic acid?
C2H5COOH (propanoic acid) = C2H5COO- + H+
- reversible reaction, as carboxylic acids are weak, so don’t lose all of their hydrogens
- they form negative ions, and their names end in ‘anoate’. so propanoic acid forms propanoate ion and a hydrogen ion
- it is always the hydrogen attached to the OH group that ionises. the other hydrogen atoms are strongly bonded to the carbon atoms
describe the reaction of a carboxylic acid with a metal carbonate:
carboxylic acid + metal carbonate = salt + water + carbon dioxide.
- this is like any other acid reaction with a metal carbonate
e.g. ethanoic acid + potassium carbonate = potassium ethanoate + water + carbon dioxide.
what other acid/base reactions do carboxylic acids partake in?
(keep in mind they react like any other acid)
carboxylic acid + metal = salt + hydrogen
carboxylic acid + metal oxide = salt + water
carboxylic acid + metal hydroxide = salt + water
how are carboxylic acids made?
take an alcohol (e.g. butanol) and oxidise it, using an oxidising agent (which adds in oxygen). this forms a carboxylic acid (e.g. butanoic acid)
describe the form of the carboxylic acid functional group:
the C has a double bond with one of the oxygens and a single bond with the other. this other oxygen forms a single bond with a hydrogen
- this entire functional group is usually on the end of what looks similar to an alkane
what is the general formula for carboxylic acids?
CnH2n+1COOH
describe esters:
- their functional group is COO. can also be called ester group/ester link/ester bond - links together carboxylic acid and alcohol, so it’s usually somewhere in the middle of the molecule
- pleasant smell - sweet/fruity. used in perfumes, food colourings/flavourings.
- volatile (evaporates quickly) - makes it good for perfumes, as you then buy more.
- also used in nail polish removers, glue, and decaf drinks.
how do you make esters?
carboxylic acid + alcohol (acid catalyst, typically concentrated sulfuric acid) = ester + water
e.g. ethanoic acid + ethanol = ethyl ethanoate + water
- the water is a by-product, formed from the OH from the carboxylic acid and the H from the ethanol.
what are addition polymers formed from?
polymers are formed from alkenes. for example, if you lined up three ethene molecules next to each other, their carbon-carbon double bonds could split open to connect to their adjacent molecules.
- this forms one long chain (a polymer)
how would you show the reaction of an alkene becoming an addition polymer?
draw a single monomer on the left, and a single repeating unit of the polymer on the right. put both units in brackets.
- draw monomer bonds up and down, instead of out at angles.
- for the polymer, draw the empty bonds pointing out through the left and right, passing through the brackets.
- put n’s outside of the brackets, showing how many monomers and repeating units there are. for the monomer, put a big n central to the left of the bracket, for the polymer, put a small n to the bottom right of the bracket
how do you name a polymer?
put the word ‘poly’ in front of the monomer’s name. put the monomer name in brackets.
- e.g. ‘butene’ becomes ‘poly(butene)’
what are condensation polymers and how are they formed?
- made up of many individual monomers.
- they’re usually made up of 2 different types of monomers.
- dicarboxylic acid monomer
(contains 2 carboxylic acid groups)
- diol monomer (2 alcohol groups) - process forms water molecules.
- dicarboxylic acid must give up OH group. diol must give up hydrogen atom from its OH group. these three atoms combine to form a water molecule.
- this leaves a carbon from the dicarboxylic acid to bond directly to an oxygen from the diol monomer, forming a bond which we call the ‘ester link’ - COO.
- at this point, the molecule is just a dimer, as it’s only two molecules combined.
- to show it as a polymer, remove an OH and an H atom from the ends, forming another water molecule. these carbon bonds can now stick through brackets and form a polymer, by bonding on to other repeating units.
what is the reaction equation for polyester?
dicarboxylic acid + diol monomer = condensation polymer (e.g. polyester) + 2H2O
- as this process often occurs with hundreds or thousands of monomers, place an n in front of each reactant and product, instead of writing the exact number of molecules we have:
e.g. n dicarboxylic acid monomer + n diol monomer = condensation polymer (polyester) n + 2n H2O
- place the n in the bottom right corner of the condensation polymer in brackets, place the n in front of the other molecules
what do molecules require to be able to combine in condensation polymers?
- each of the monomers has to have at least two functional groups.
- e.g. dicarboxylic acid monomers have
two COOH functional groups, diol
monomers have two OH functional
groups.
- e.g. dicarboxylic acid monomers have
- must be at least two different functional groups overall.
- e.g. has one carboxyl group and one
alcohol group.
- e.g. has one carboxyl group and one
- a small molecule is given off in the process.
- e.g. generally water.
why are polyesters (condensation polymers) biodegradable?
they can break down naturally because bacteria and other micro-organisms can break down the ester links.
- this is the big difference to addition polymers, which are usually plastics, so aren’t biodegradable.
what are naturally existing polymers?
polymers that exist naturally in an environment and aren’t man-made
- e.g. polypeptides, DNA, carbohydrates
what are polypeptides and how are they linked to proteins?
- amino acids in one long chain are called polypeptides.
- when the polypeptide folds up or combines with other polypeptides, we call it a protein.
- as there are many types of amino acids, and they can combine in many different ways, this results in a wide range of proteins that can do a wide range of things.
- it can catalyse chemical reactions (enzymes)
- provide structure and strength to tissues in our bodies.
what is the structure of an amino acid?
- always contains a carboxyl group (COOH), and an amino group (H2N)
- always joined together by a central carbon.
- there is a group at the bottom, connected to the central C, called an ‘R’ group, which changes depending on which amino acid it is, making all amino acids different.
how do amino acids join together to form a polymer?
- the amino and carboxyl functional groups of the amino acid allows adjacent amino acids to join together through condensation reactions.
- the OH from the carboxyl group and the H from the amino group react together to produce water.
- the amino acids now join together, as the carbon on the carboxyl functional group and the nitrogen on the amino group can bond.
- this bond can be called an ‘amide bond’, an ‘amide link’ or a ‘peptide bond’.
describe DNA:
- monomers are structures called nucleotides. they all contain a small molecule called a base. the rest of the nucleotide stays the same
- by combining these 4 different nucleotides in different orders, our cells can make different codes, which we call genes.
- to keep these codes intact and prevent them from getting damaged, DNA is made of two polymer chains linked together, and this double strand naturally coils to form a double helix
what are the four types of bases on a nucleotide?
represented by the letters:
- T
- A
- G
- C
describe carbohydrates:
carbohydrates = general term, refers to a number of different polymers and monomers.
- we derive energy from carbohydrates.
- they are all only made from carbon, hydrogen and oxygen.
- the polymers (called polysaccharides) are things like starch, cellulose, and glycogen.
- the monomers (monosaccharides or sugars) are things like glucose and fructose.
- by combining the monomers together, we can make the polymers. by combining lots of glucose, we can make starch, for instance.
what are isomers?
molecules that have the same molecular formula, but different structural formulas: made of the same atoms, but the atoms are arranged differently, so they have different names
describe the complete combustion of alkanes:
hydrocarbon + oxygen = carbon dioxide + water (+energy)
- therefore it’s exothermic
- the hydrogen and oxygen in the hydrocarbon are being oxidised
- complete combustion only occurs when there is sufficient oxygen
how do you balance an equation when there is an odd number of atoms on one side?
double everything, so the number is even and much nicer to balance
what is a feedstock?
a raw material used to provide reactants for an industrial reaction (different hydrocarbons in crude oil)
what is a petrochemical?
a substance made from crude oil via chemical reactions (polymers, solvents, lubricants, detergents)
