Organic Chemistry

• Organic chemistry

  Chemistry of compounds containing carbon
• Carbon

  • Useful for making large compounds
  • Can form four strong bonds
  • Most commonly bonded to other carbon atoms or hydrogen atoms
• Hydrocarbons

  Compounds formed from carbon and hydrogen only
• First four alkanes

  • Methane
  • Ethane
  • Propane
  • Butane
• Homologous series

  • Groups of organic compounds with similar properties and reactions
  • Can be described by a general formula
• Alkanes are saturated compounds, with every carbon having four single covalent bonds
• If a single bond in an alkane is changed to a double bond

  It would no longer be an alkane, but an alkene
• Isomers

  Isomers are molecules that have the same molecular formula, but different structural formulas, this means they are made of the same atoms, but the atoms are arranged differently.
• Which Alkane is shown below?

  Methane

  
• Which alkane is shown below?

  Ethane

  
• Which alkane is shown below?

  Propane

  
• Which alkane is shown below?

  Butane

  
• Alkanes

  A homologous series of hydrocarbons that contain only carbons and hydrogen atoms with no double bonds
• Alkanes

  • As the length of the carbon chain increases:
  • Boiling point increases
  • Shorter alkanes are more volatile and evaporate more easily
  • Longer alkanes are more viscous and thick
  • Shorter alkanes are more flammable and easier to ignite or burn
• Combustion reactions

  1. Hydrocarbon reacts with oxygen

  2. Forms carbon dioxide and water

  3. Releases energy (exothermic)
• Complete combustion

  Hydrocarbon reacts with enough oxygen to form carbon dioxide and water
• Hydrocarbons like alkanes are used as fuels because they release energy when combusted
• Crude oil

  A fossil fuel that we get from deep under the ground, a mixture of lots of different compounds
• Crude oil

  • Nearly all of the compounds are hydrocarbons which contain only hydrogen and carbon
  • The most common type of hydrocarbons are alkanes
• Formation of crude oil

  1. Remains of dead plants and animals, particularly plankton, buried in the mud

  2. High pressures and temperatures under the ground turned this organic biomass into crude oil

  3. Crude oil soaked into the rocks and was stored for millions of years
• Crude oil is a finite resource
• Fractional distillation

  A process used to separate the different hydrocarbons in crude oil by making use of their different boiling points
• Fractional distillation

  1. Feed the oil into a chamber and heat it until most of it has turned into a gas

  2. Pass the gaseous mixture into a fractionating column which is hot at the bottom but gets cooler towards the top

  3. Hydrocarbons with the longest chains condense first and drain out early

  4. Shorter chain hydrocarbons stay gaseous longer and condense at higher points in the column
• Fractions obtained from fractional distillation

  • Bitumen
  • Heavy fuel oil
  • Diesel
  • Petrol
  • Kerosene
  • LPG (propane and butane)
• Fractions from fractional distillation

  • Shorter chain hydrocarbons are more flammable and make better fuels
  • Longer chain hydrocarbons are often poor fuels and may need to be broken down further
• Petrochemicals

  Substances obtained from crude oil that can be used as feedstock (raw materials) for the petrochemical industry to make things like solvents, lubricants, polymers and detergents
• Feedstock

  A feedstock is a raw material used to provide reactants for an industrial reaction.
• The different hydrocarbons in crude oil are all feedstocks, but the useful things we then make from those hydrocarbons (polymers, solvents, lubricants, detergents etc.), are all petrochemicals. 
• Crude oil

  A mixture of lots of different hydrocarbons
• Fractional distillation

  Separates out different hydrocarbons by the length of their carbon chains
• Shortest hydrocarbons

  • Most flammable, make the best fuels
• Longer chain hydrocarbons

  • Thick viscous liquids, comparatively less useful
• Cracking

  Breaks down longer less useful hydrocarbons into shorter more flammable hydrocarbons
• Thermal decomposition

  Breaking down molecules by heating them
• Cracking methods

  • Catalytic cracking
  • Steam cracking
• Catalytic cracking

  Heat long chain hydrocarbons and vaporize, pass over hot powdered aluminium oxide catalyst which splits apart into two smaller hydrocarbons
• Steam cracking

  Vaporize hydrocarbons, mix with steam, heat to very high temperature which causes long hydrocarbon chains to split apart into shorter ones
• Balanced chemical equation for cracking long chain alkanes

  Long chain alkane (e.g. decane) goes to form shorter alkane (e.g. heptane) and alkene (e.g. propene)
• Number of carbons and hydrogens on each side of the equation must be the same
• Alkenes

  • More reactive than alkanes
  • Can be added together to make polymers