Organic Chemistry

• Crude oil is a finite resource found in rocks
• Crude oil is the remains of an ancient biomass consisting mainly of plankton that was buried in mud
• Mixture


  2 or more elements that are not chemically combined
• The chemical properties of each substance in the mixture are unchanged
• It is possible to separate the substances in the mixture by physical methods including distillation
• Most of the compounds in crude oil consist of molecules made up of hydrogen and carbon only (hydrocarbons)
• Most of these saturated hydrocarbons are alkanes
• Hydrocarbons- alkanes


  Have the general formula: CnH2n+2
• First 4 alkanes


  • Methane
  • Ethane
  • Propane
  • Butane

  
• Fractional distillation


  1. Oil is heated in the fractionating column and the oil evaporates and condenses at a number of different temperatures

  2. The many hydrocarbons in crude oil can be separated into fractions each of which contains molecules with a similar number of carbon atoms

  3. The fractionating column works continuously, heated crude oil is piped in at the bottom and the vaporised oil evaporates and rises up the column and the various fractions are constantly tapped off at the different levels where they condense
• The fractions can be processed to produce fuels and feedstock for the petrochemical industry
• Fuels produced from crude oil


  • Petrol
  • Diesel oil
  • Kerosene
  • Heavy fuel oil
  • Liquefied petroleum gases
• Many useful materials on which modern life depends are produced by the petrochemical industry, such as solvents, lubricants, polymers, and detergents
• The vast array of natural and synthetic carbon compounds occur due to the ability of carbon atoms to form families of similar compounds
• Properties of hydrocarbons


  • Shorter the molecules, the less viscous it is (more runny)
  • The longer the molecules, the more viscous it is
  • The shorter the molecules, the lower the temperature at which that fraction is vaporised or condensed - and the lower its boiling point
  • The shorter the molecules, the more flammable it is
• Burning hydrocarbons


  1. Hydrocarbon -> carbon dioxide + water

  2. The hydrogen and carbon are oxidised in the reaction
• Cracking hydrocarbons


  1. Passing them over a hot catalyst (catalytic cracking)

  2. Mixing them with steam and heated to a very high temperature so that thermal decomposition reactions can occur (steam cracking)
• Alkenes


  Unsaturated hydrocarbons with the general formula CnH2n and have at least one double carbon-carbon bond

  
• First 2 alkenes


  • Ethene
  • Propene

  
• Alkenes react with bromine water, turning it from orange to colourless, alkanes do not
• Alkenes are used for producing other chemicals (e.g. polymers)
• Some of the products made from cracking are useful as fuels, since they have shorter chains than the alkanes you started with, making them more flammable so a better fuel
• Cracking equations


  1. You must make sure there are the same number of carbons and hydrogens on each side of the equation

  2. You are going from a bigger molecule to usually 2 smaller molecules