Alkanes

• Crude oil is a mixture of different hydrocarbons
• Crude oil can be separated into separate molecules by fractional distillation
• Different chain lengths of molecules result in different boiling points
• Fractional distillation process:

  • The mixture is vaporized and fed into the fractionating column
  • Vapors rise, cool and condense
  • Products are siphoned off for different uses
  • Products with short carbon chains have lower boiling points and are collected at the top of the column
  • Products with long carbon chains have higher boiling points and are collected at the bottom of the column
• Compounds collected from the fractionating column are further broken down via cracking
• Cracking:

  • Longer carbon chains are broken down to form smaller, more useful molecules
  • Carbon-carbon bonds are broken under harsh reaction conditions
  • Two main types of cracking: Thermal Cracking and Catalytic Cracking
  • Thermal Cracking produces alkanes and alkenes at high temperatures and pressures
  • Catalytic Cracking produces aromatic compounds with a zeolite catalyst at lower temperatures
• Alkanes make good fuels as they release a lot of energy when burned
• With sufficient oxygen, alkanes undergo complete combustion to produce carbon dioxide and water
• Incomplete combustion of alkanes can produce carbon monoxide and water
• Carbon monoxide is a toxic gaseous product produced from incomplete combustion of alkanes
• Catalytic converters use a rhodium catalyst to convert harmful products into more stable products like CO2 or H2O
• Incomplete combustion can produce carbon particulates, which can cause respiratory problems if not removed
• Sulfur impurities can lead to acidification of water in the Earth's atmosphere and can be removed via flue gas desulfurization using calcium oxide and gypsum
• Pollutants from incomplete combustion and sulfur impurities can contribute to global warming, acid rain, and health issues in humans
• Alkanes react with halogens in the presence of UV light to produce halogenoalkanes
• UV light breaks down halogen bonds to produce free radicals that attack alkanes in a series of reactions: initiation, propagation, and termination
• Chain reaction can result in multiple substitutions
• Reaction conditions can be altered to favor the termination step and limit the number of substitutions