Alkanes

• Fermentation

  C6H12O6 -> 2CO2 + 2C2H5OH

  Conditions:

  • Anaerobic - no oxygen present
  • 25c-40c
  • yeast

  Distillation is used to separate ethanol from yeast

  Hydration:

  Ethane + Water ⇌ Ethanol

  Conditions:

  • Steam
  • 300C
  • 6000kPa
  • Acid catalyst: phosphoric acid
• Conditions for thermal cracking and what kind of products:

  • High pressure → 7000 kPa
  • High temperature → 700 degrees c
  • Products: short chain alkenes
• Conditions for catalytic cracking and products:

  • 450 °C
  • Slight pressure
  • Zeolite catalysts
  • cycloalkanes, branched alkanes and aromatic compounds
• What are fuels? Compounds that release heat energy when burnt
• What are alkanes used as? Fuels
• What can soot cause? Global dimming - reflection of the sun's light
• Internal combustion engines produce the following pollutants:

  • NOx 
  • CO
  • unburned hydrocarbons
  • SOx
• SO2 can be removed from waste gases produced from furances through ... flue gas desulfurisation
• What are the 3 main greenhouse gases?

  1. Carbon Dioxide
  2. Methane
  3. Water Vapour
• What are the 3 steps of free radical substitution?

  • Initiation
  • Propagation
  • Termination
• Nucleophile: electron pair doner
• Electrophile: electron pair acceptor
• What does the Ozone layer do?

  Filters out most UV radiation
• Why are CFC's harmful to the ozone layer?

  Chlorine radicals form and catalyse the breakdown of ozone to oxygen
• Strongest intermolecular force of alkanes?

  Van der waals
• Trends in alkanes:

  As chain length increases boiling point increases

  This is because there are more electrons for stronger van der waal forces
• What is the reactivity of alkanes and why?

  Generally inert due to non-polar bonds caused by similar electronegativity between C and H
• Complete Combustion:


  • Excess oxygen   
  • Products are CO2 and H2O
• Incomplete Combustion:

  • Limited oxygen
  • Products are CO and H2O and sometimes C (soot)
• What is the environmental impact of nitrogen oxides? form nitric acid → acid rain, photochemical smog
• Write an equation for the overall decomposition of ozone into oxygen (O2):2O3 → 3O2
• What is a petroleum fraction? A mixture of hydrocarbons with a similar chain length and similar boiling point
• Cracking:

  • conversion of large hydrocarbons to smaller, more useful hydrocarbon molecules
  • by breaking C-C bonds
• What are the two types of cracking? Catalytic and Thermal
• Nucleophilic Substitution reaction process:

  1. Nucleophiles attack positive carbon atom
  2. Carbon atom has a delta positive charge due to electronegativity difference between the halogens and carbon
  3. nucleophile replaces the halogen, to form a new compound + halogen free radical 
• What is the process of converting alkanes to haloalkanes?

  Free radical substitution
• What is the environmental impact of nitrogen oxides? form nitric acid → acid rain, photochemical smog
• state the 2 factors affecting the strength of van der waal forces?

  amount of electrons (greater distortions)

  points of contact between molecules
• Complete combustion occurs when there is excess oxygen and the products are carbon dioxide and water
• Incomplete combustion occurs when there is limited oxygen and the products are C, known as soot, CO, carbon monoxide, and H2O