Organic chemistry

• hydrocarbons only contain hydrogen and carbon atoms
• alkanes have a single bond 


  the formula for alkanes is CnH2n+2

  are homologous series and saturated compounds
• alkanes


  methane

  ethane

  propane

  butane

  pentane
• hydrocarbon properties change when it gets longer

  the shorter the carbon chain, the more runny it is (less viscous)

  the shorter the carbon chain, the more volatile it is (turns into gas at a lower temperature)

  the shorter the carbon chain, the more flammable the hydrocarbon is
• complete combustion occurs in oxygen 


  the complete combustion of any hydrocarbon in oxygen releases lots of energy with the only waste products are carbon dioxide and water

  hydrocarbon + oxygen = carbon dioxide + water

  both are oxidised

  hydrocarbons are used as fuels due to the amount of energy released when they combust
• crude oil is a fossil fuel

  it is formed from the remains of plants and animals, mainly plankton, that died millions of years ago and were buried in mud. over millions of years, with high temperatures and pressure, the remains turn to crude oil, which can be drilled up from rocks
• fossil fuels are non-renewable


  they are being used faster than they are being used

  they are finite resources- one day they will run out
• fractional distillation is used to separate hydrocarbon fractions


  crude oil is a mixture of lots of different hydrocarbons, most of which are alkanes

  the different compounds in crude oil are separated by fractional distillation
• fractional distillation 


  the oil is heated until most of of it has turned into gas, the gas enters a fractionating column. in the column there is a temperature gradient.

  the longer hydrocarbons have high boiling points. they condense into liquids and drain out of the column. the shorter hydrocarbons have shorter boiling points, they condense and drain out later on. the crude oil is separated into different fractions. each fraction contains a mixture of hydrocarbons that all contain a similar number of carbon atoms so have similar boiling points
• crude oil has various uses

  oil provides fuel for most transport- cars, trains, planes

  the petrochemical industry uses some of the hydrocarbons from crude oil as a feedstock to make new compounds for use in things like polymers, solvents, lubricants, and detergents

  the products produced from crude oil are organic compounds
• cracking is splitting up long chain hydrocarbons

  short chain hydrocarbons are flammable and so make god fuels and are in high demand. long chain hydrocarbons form thick gloopy liquids like tar which aren't very useful

  a lot of the longer alkane molecules produced from factional distillation are turned into smaller more useful ones through cracking

  cracking also produces alkenes which can be used as a starting material when making lots of other compounds and can be used to make polymers.
• cracking 


  cracking is a thermal decomposition reaction- breaking down molecules by heating them. the first step is to heat long-chain hydrocarbons to vaporise them. the vapour can be passes over a catalyst (hot powdered aluminium oxide). the long-chain molecules split apart on the surface on the specks of catalyst- catalytic cracking

  steam cracking- vaporise them, mix them with steam, and then heat them to a very high temperature
• alkenes have a double bond

  they have two fewer hydrogens than alkanes making them unsaturated

  alkenes are far more reactive than alkanes

  formula CnH2n
• alkenes


  ethene

  propene

  butene

  pentene
• alkenes burn with a smoky flame

  in a large amount of oxygen, alkenes combust completely- often incomplete combustions in air

  alkene + oxygen = carbon + carbon monoxide + carbon dioxide + water

  incomplete combustion results in a smoky yellow flame and less energy than complete combustion
• alkenes react via addition reactions


  a functional group is a group of atoms in a molecule that determines how much that a molecule typically reacts. all alkenes have the same functional group so react in similar ways so the products of a reaction can be predicted

  the carbon double bond will open up to leave a single bond and a new atom is added to each carbon
• addition of hydrogen is known as hydrogenation


  hydrogen can react with the double-bonded carbon to open up the double bond and form an alkane.

  the alkene is reacted with hydrogen in the presence of a catalyst

  nickel at 60C
• halogens can react with alkenes


  alkenes will also react in addition reactions with halogens such as bromine and chlorine. these molecules are saturated

  bromine and ethene react together to form dibromoethane
• alkenes turn bromine water colourless


  when orange bromine water is added to a saturated compound no reaction will happen and it will stay bright orange

  if an alkene is added to bromine water, the bromine will add across the double bond making a colourless dibromo-compound so the bromine water is decolourised
• steam can react with alkenes to form alcohols


  water is added across the double bond and an alcohol is formed
• plastics are made up of long-chain molecules called polymers


  polymers are long molecules formed when lots of small molecules called monomers join together- polymerisation which needs a high temperature and a catalyst

  plastics are made up of polymers, they are usually carbon based and their monomers are usually alkenes
• addition polymers are made from unsaturated monomers


  the monomers that make up addition polymers have a double covalent bond. lots of unsaturated monomer molecules can open up their double bonds and join together to form polymer chains- addition polymerisation

  when the monomers react the only product is the polymer so an addition polymer contains the same type and number atoms as the monomers that formed it
• alcohols have an -OH functional group

  methanol

  ethanol

  propanol

  butanol
• alcohols are flammable 


  they undergo complete combustion in the air to produce carbon dioxide and water

  alcohols can be oxidised by reacting with oxygen to produce a carboxylic acid
• alcohols are used as solvents and fuels


  they can dissolve most things water can dissolve but also dissolve substances that water cannot dissolve

  the first four alcohols are used as fuels- ethanol is used as fuel in spirit burners and it burns fairly cleanly and is non-smelly
• ethanol can be made by fermentation

  fermentation uses an enzyme in yeast to convert sugars into ethanol

  carbon dioxide is also produced. the reaction occurs in solution so the ethanol produced is aqueous

  sugar =(yeast)= ethanol + carbon dioxide

  fermentation happens fastest around temps of 37 in slightly acidic conditions and anaerobic conditions
• carboxylic acids have the functional group - COOH

  their names end in -anoic acid

  methanoic acid

  ethanoic acid

  propanoic acid

  butanoic acid
• carboxylic acid react like other acids

  they react with carbonates to produce a salt, water, carbon dioxide

  the salts formed in these reactions end in -anoate

  carboxylic acids can dissolve in water
• esters can be made from carboxylic acids

  esters have the functional group -COO

  they are formed from an alcohol and a carboxylic acid

  an acid catalyst is used

  alcohol + carboxylic acid = ester + water
• ethyl ethanoate
• condensation polymers 


  involve monomers which contain different functional groups

  the monomers react together and bonds form between them, making polymer chains

  for each new bond that that form small molecule is lost

  the simplest types of condensation polymers contain two types of monomer, each with two of the same functional groups
• addition polymers


  only one monomer type containing a double carbon bond

  only one product formed

  carbon-carbon double bond in monomer
• condensation polymerisation 


  two monomer types each containing two of the same functional groups or monomer type with two different functional groups

  two types of product- the polymer and a small molecule

  two reactive groups on each monomer
• an amino acid contains two different functional groups


  a basic amino group and a acidic carboxyl group

  glycine- the smallest and simplest amino acid possible
• proteins are polymers of amino acids

  amino acids can form polymers known as polypeptides via condensation polymerisation. the amino group of an amino acid can react with the acid group of another and so on, to form a polymer chain

  one or more long-chain of polypeptides are known as proteins. proteins have lots of important uses in the human body

  polypeptides and proteins can contain different amino acids in their polymer chains. the order is what gives proteins its properties + shapes
• DNA molecules are made from nucleotide polymers


  DNA (deoxyribonucleic) is found in every living thing and many viruses.

  it contains genetic instructions that allow the organism to develop and operate. it is a large molecule that takes a double helix structure
• DNA 


  made of two polymer chains of monomers called nucleotides. the nucleotides contain a small molecule known as a base. There are four different bases known as A,C,T,G

  the bases on the different polymer chains pair up with each other and form cross links, keeping the two strands of nucleotides together and giving the double helix structure

  the order of the bases acts as a code for an organism's genes
• simple sugars can form polymers


  sugars are small molecules that contain carbon, oxygen, and hydrogen

  sugars can react together through polymerisation reactions to form larger polymers, which living things use to store energy, and cellulose, which is found in plant cell walls