Organic Chemistry

• alkane general formula

  CnH2n+2
• complete combustion


  hydrocarbon + oxygen -> carbon dioxide + water vapour
• crude oil

  • a mixture of many compounds
  • formed over millions of years, mainly from plankton
  • a mixture of mainly hydrocarbons which are mainly alkanes
• order of fractional distillation products, highest up to lowest

  Liquified petrol gas

  Petrol

  Kerosene

  Diesel

  Heavy fuel oil

  Bitumen
• Hydrocarbon properties

  Shorter chain means lower boiling point and higher flammability

  longer chain means more viscous
• alkanes are saturated hydrocarbons and the most simple form of them
• hydrocarbon

  any molecule containing only hydrogen and carbon
• alkene general formula

  CnH2n
• alkenes

  • more reactive than alkanes
  • carbon carbon double bond
  • unsaturated which means they are more reactive
• incomplete combustion

  alkene + oxygen -> carbon + carbon monoxide + water

  results in a smokey yellow flame
• combustion in alkenes

  complete combustion only happens when the alkene is in a lot of water

  incomplete combustion happens when the alkene is burnt in air
• thermal decomposition 


  breaking down the molecules with heat
• Catalytic cracking


  vapourised hydrocarbon is passed over a hot, powdered catalyst
• steam cracking


  vapourised hydrocarbon is mixed with steam at a very high temperature
• cracking

  breaking down long chain hydrocarbons into shorter chain hydrocarbons because these tend to be more useful

  products: alkanes and alkenes
• mnemonic to remember products of the fractional distillation of crude oil

  Leave

  Poor

  Kelvins

  Donkey (to)

  Happily

  Birth
• reactions of alkenes:

  addition reaction:

  • breaks down the C=C

  hydrogenation

  • turns alkenes into alkanes
  • alkene + H-H -> alkane

  forming alcohols

  • alkene + steam + catalyst -> alcohol

  addition of halogens

  • eg ethene + bromine -> dibromoethane
• addition polymers

  small alkene monomers join together, breaking the double bond, to form a long chain polymer

  high pressure and a catalyst are needed

  (below) is the displayed structural formula of poly(ethene)

  
• alcohols


  -OH functional group

  CnH2n+1OH

  uses:

  • alcoholic drinks - mainly ethanol
  • solvents - dissolved things water does not such as fats
  • fuels - ethanol is used in spirit burners, pure ethanol burns clean and non smelly

  properties:

  • flammable (produce CO2 and water when burnt in air)
  • dissolve completely in water to form neutral solution
  • react with sodium
  • oxidise to form carboxylic acids
• fermentation


  sugar (+yeast) -> carbon dioxide + ethanol

  how ethanol is made for alcoholic drinks

  conditions:

  • 37C
  • slightly acidic
  • anaerobic
• carboxylic acids


  -COOH

  properties:

  • react like other acids
  • partially ionise in water (weak acid)
  • dissolve in water

  
• esters

  have fruity smells and can be used as solvents

  alcohol + carboxylic acid -> ester + water (use a strong acid catalyst)

  -COO-

  one name to know: ethyl ethanoate
• condensation polymers


  monomers with different functional groups joined together to make a polymer

  for each new bond, a small molecule (water) is lost, hence the name
• naturally occurring polymers


  amino acids:

  • have two functional groups: basic amino group (NH2) and acid carboxyl group (COOH)
  • form polypeptides which are a protein

  DNA:

  • nucleotides are the monomers

  sugars:

  • contain carbon, hydrogen and oxygen
  • such as cellulose and starch