Organic

• 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
• Hydrocarbons


  • Butane
  • Butanol (not a hydrocarbon as it contains oxygen)
• 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
• Changing an alkane to have a double bond would make it an alkene, not an alkane
• Alkanes


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


  • Similar properties
  • Boiling point increases with chain length
  • Shorter alkanes are more volatile and flammable
  • Longer alkanes are more viscous
• 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
• Combustion equations


  • Propane (C3H8)
  • Nonane (C9H20)
• Hydrocarbons like alkanes are used as fuels because they release energy when combusted
• Fractional distillation


  Separates hydrocarbons by length of carbon chains
• 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, vaporize, pass over hot powdered aluminium oxide catalyst which splits them into smaller hydrocarbons
• Steam cracking


  Vaporize long chain hydrocarbons, mix with steam, heat to high temperature to split into smaller hydrocarbons
• 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 must balance on both sides of the equation
• Alkenes


  • Unsaturated, more reactive than alkanes, can be added together to make polymers
• Adding bromine water to alkenes

  Decolorizes the bromine water from orange to colourless, test for alkenes
• Decane (C10H22) can be cracked into ethene (C2H4) and one other hydrocarbon
• Cracking decane


  Decane (C10H22) goes to form ethene (C2H4) and an alkane with 8 carbons (C8H18)
• Alkenes


  Unsaturated hydrocarbons that contain at least one carbon-carbon double bond
• Alkenes


  • They can undergo addition reactions due to their carbon-carbon double bond
  • The double bond can open up and allow the two carbons to bond to atoms of another molecule
• Addition reactions of alkenes

  1. With hydrogen

  2. With water

  3. With halogens
• Propine


  An alkene with a 3 carbon chain
• Reaction of propine with hydrogen

  1. Double bond breaks apart

  2. Hydrogen atoms bond to the carbons

  3. Product is propane (an alkane)
• Ethene


  An alkene
• Reaction of ethene with water

  1. Double bond opens up

  2. Water molecule splits into hydrogen and OH group

  3. Hydrogen and OH group bond to the carbons

  4. Product is ethanol (an alcohol)
• Ethanol is the same alkyl used in alcoholic drinks and some industrial processes
• Separating ethanol from unreacted ethene and water

  1. Ethene has low boiling point, so it stays as gas

  2. Water and ethanol condense into liquid

  3. Fractional distillation separates water and ethanol
• Reaction of alkenes with halogens

  1. No catalyst required

  2. Most common is reaction with bromine

  3. Bromine decolorizes from orange to colorless
• Alkenes can decolorize bromine water, while alkanes cannot
• Alcohols


  Organic compounds with an -OH group in place of one of the hydrogen atoms
• Alcohols


  • They are a homologous series
  • Their names end in -ol instead of -ane
• First four alcohols in the homologous series

  • Methanol
  • Ethanol
  • Propanol
  • Butanol