C7 - Organic chemistry

An overview of the information in C7

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Hydrocarbon alkanes

  • Made up of only hydrogen and carbon atoms
  • Formula for hydrocarbons is Cn H2n+2
  • e.g. methane = CH4, Ethane = C2H6, propane = C3H8, Butane = C4H10
  • Properties include:
    • unreactive with water
    • oily
    • burn well in plenty of oxygen with the formula: Alkene + O2 --> CO2 +H2O
    • e.g. C2H6 (g) + 3.5 O2 (g) --> 2 CO2 (g) + 3 H2O (l)
    • Does not react with sodium
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  • Have the functional group -OH, giving alcohols their characteristics
  • Formula for alcohols is Cn H2n+1 OH
  • e.g. methanol = CH3OH, ethanol = C2H5OH
  • Both can be used as fuels and to manufacture solvents
  • Properties include:
    • combust in oxygen because of the hydrocarbon chain with the formula: alcohol + O2 --> H2O + CO2
    • have stronger attractions between molecules so have higher boiling points than alkanes
    • longer molecules are more oily
    • reacts with sodium less violently than water
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Carboxylic acids

  • Have the functional group COOH with gives carboxylic acids their characteristics
  • formula for carboxylic acids is Cn-1H2n-1COOH
  • e.g methanoic acid = HCOOH, ethanoic acid = CH3COOH
  • Properties include
    • very unpleasant smells and tastes
    • are weak acids
    • can be neutralised by metals alkalis and carbonates
  • e.g. Ethanoic acid + sodium --> sodium ethanoate + Hydrogen,
  • Methanoic acid + sodium carbonate --> sodium methanoate + water + carbon dioxide
  • Carboxylic acids are found in:
    • vinegar - dilute ethanoic acid
    • rancid butter
    • sweaty socks/ feet - butanoic acid
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  • Carboxyilic acids and alcohols react in the presence of a strong acid catalyst, to form esters
  • e.g. Methanol + ethanoic acid  --(sulfuric acid)--> methyl ethanoate + water
  • Esters are prepared by:
    • mixing an alcohol and excess carboxylic acid and heating them in reflux (under a condenser) in the presence of concentrated sulphuric acid
    • distilling this mixture by heating it and using a condenser as esters have lower boiling points than most other substances
    • In a separating funnel, sodium carbonate is added, reacting with any remaining acid and extracting it to an aqueous phase, which is run off
    • In a conical flask, a drying agent is added to remave and remaining water, which is later removed by filtration.
  • Estersd have distinctive, sweet smells and are found in perfumes and food products as well as naturally occuring in fruits
  • They are also found in solvents like adhesives and plasticisers because of their hydrocarbon chains
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