Topic 7

• 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
• Separating substances in crude oil mixture

  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


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


  • Methane
  • Ethane
  • Propane
  • Butane

  
• Fractional distillation


  Oil is heated in the fractionating column and the oil evaporates and condenses at different temperatures
• The many hydrocarbons in crude oil can be separated into fractions each of which contains molecules with a similar number of carbon atoms
• The fractionating column works continuously, with heated crude oil piped in at the bottom
• The various fractions are constantly tapped off at the different levels where they condense
• Fuels produced from crude oil fractions

  • Petrol
  • Diesel oil
  • Kerosene
  • Heavy fuel oil
  • Liquefied petroleum gases
• Materials produced by the petrochemical industry

  • Solvents
  • Lubricants
  • Polymers
  • Detergents
• Alkenes


  Hydrocarbons with the functional group C=C

  
• The vast array of natural and synthetic carbon compounds occur due to the ability of carbon atoms to form families of similar compounds
• Viscosity


  How runny a hydrocarbon is
• Shorter the hydrocarbon molecules

  Less viscous it is
• Longer the hydrocarbon molecules

  More viscous it is
• Shorter the hydrocarbon molecules


  Lower the temperature at which that fraction is vaporised or condensed, and the lower its boiling point
• Addition polymerisation


  1. Alkenes can be used to make polymers such as poly(ethene) and poly(propene)

  2. Many small molecules (monomers) join together to create very large molecules (polymers)
• Shorter the hydrocarbon molecules

  More flammable it is
• Burning hydrocarbons


  1. Hydrocarbon -> carbon dioxide + water

  2. 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 heating to a very high temperature so that thermal decomposition reactions can occur (steam cracking)
• First 4 alkenes


  • Ethene
  • Propene
  • Butene
  • Pentene
• Alkenes


  Unsaturated hydrocarbons produced by cracking, with the general formula CnH2n and at least one double carbon-carbon bond

  
• First 2 alkenes


  • Ethene
  • Propene
• Alkenes react with bromine water, turning it from orange to colourless, while alkanes do not
• Alkenes are used for producing other chemicals (e.g. polymers)
• Products of cracking are useful as fuels as they have shorter chains than the alkanes you started with, making them more flammable
• Repeat unit


  Has the same atoms as the monomer because no other molecule is formed in the reaction
• Cracking reaction equations


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

  2. Going from a bigger molecule to usually 2 smaller molecules
• Unsaturated carbons


  • Can be represented in the following forms:
• When drawing a polymer, remember to draw the bonds coming off the Cs out the brackets and the little 'n' (means there are large numbers of these molecules joined together)
• Alkenes react with oxygen in combustion reactions in the same way as other hydrocarbons, but they tend to burn in air with smoky flames because of incomplete combustion (meaning carbon or carbon monoxide is formed (CO))
• Reactions of alkenes


  1. React with hydrogen

  2. React with water

  3. React with halogens
• Condensation polymerisation


  1. Involves monomers with two functional groups

  2. When they react, they join together, usually losing small molecules such as water, and so the reactions are called condensation reactions

  3. Simplest polymers are produced from two different monomers with two of the same functional groups on each monomer
• Polyester


  • 1 monomer with 2 carboxylic acid functional groups and 1 monomer with 2 alcohol functional groups
• In reactions with hydrogen, water and halogens

  • The C=C bond is broken to form a C-C bond
  • The compound added splits into two groups and the two groups are added to the 2 different carbons in the C=C bond (each group can be added to either carbon)
  • H2 splits into 2 H's, H2O splits into a H and an OH, Br2 splits into 2 Br's (same for Cl2 or I2)