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


  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, 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
• Materials produced by the petrochemical industry

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


  The thickness or resistance to flow of a liquid
• Shorter the hydrocarbon molecules

  Less viscous it is (more runny)
• 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
• Shorter the hydrocarbon molecules

  More flammable it is
• Cracking


  1. Heating hydrocarbons to vaporise them

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

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


  Unsaturated hydrocarbons produced by cracking, have 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 equation


  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
• Alkenes


  Hydrocarbons with at least one carbon-carbon double bond, making them unsaturated

  
• First 4 alkenes


  • Ethene
  • Propene
  • Butene
  • Pentene
• Unsaturated carbons


  • Can be represented in the following forms:
• Reactions of alkenes


  Alkenes react with oxygen in combustion reactions, hydrogen, water and halogens by the addition of atoms across the carbon-carbon double bond
• Reactions of alkenes


  1. C=C bond is broken to form a C-C bond

  2. 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)

  3. 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)
• Alcohols


  Contain the functional group -OH
• First 4 alcohols


  • Methanol
  • Ethanol
  • Propanol
  • Butanol
• Reactions of alcohols


  They burn in air, dissolve in water to form a neutral solution, react with sodium to produce hydrogen and a salt, react with oxidising agents to form carboxylic acids
• Uses of alcohols


  • Methanol: chemical feedstock, in anti-freeze, to make biodiesel
  • Ethanol: the main alcohol in alcoholic drinks, used as a solvent and fuel
  • All 4 can be used as fuels
• Producing ethanol


  1. Ethanol can be produced by fermentation of sugar with yeast, using renewable sources

  2. Conditions: about 35°C, anaerobic (without oxygen) and yeast enzyme catalyst

  3. Sugar → ethanol + carbon dioxide
• Carboxylic acids


  Have the functional group -COOH
• First 4 carboxylic acids

  • Methanoic acid
  • Ethanoic acid
  • Propanoic acid
  • Butanoic acid

  
• Reactions of carboxylic acids

  They dissolve in water to produce acidic solutions, react with metal carbonates to produce carbon dioxide, a salt and water, react with alcohols in the presence of an acid catalyst to produce esters
• Carboxylic acids do not ionise completely in solutions, so do not release many H+ ions, making them weak acids