Module 1:Hydrocarbons and Basic concepts

OCR as level chemistry. F322



  • General formula CnH2n+1(OH)
  • Structural differences:


Chemical behaviour especially oxidation depends on the structural type

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Making ethanol

  • Can be made by the hydration of steam
  • Hydration of ethene C2H4 using steam in the presence of a phosphoric catalyst H3P04.
  • Carried out at a high temperature and moderate pressure.
  •  (
  • This reaction is reversible and so reaction of ethene is incomplete
  • overall a 90% conversion is achieved
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  • Another method of manufacturing alcohol
  • Carried out at low temperatures between 25 and 35. An enzyme called zymase is used.
  • Fermentation of carbohydrates to ethanol is anaerobic. If air was present,ethanol would be oxidiesed to ethanal or ethanoic acid which would affect its flavour.
  • Carbohydrates are converted into ethanol and carbon dioxide
  • ethanol can be used in perfumes and is a solvent in methylated spirits and is being developed as an alternative fuel for cars.
  • Spirits have a higher alcohol content as the fermented drink is distilled by slowly heating the alcohol-water mixture.
  • The alcohol boils off faster than the water and is then allowed to condense
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Methanol and Methylated spirits

  • Methylated spirits is undrinkable and tax exempt because it consists of ethanol mixed with small amounts of methanol and coloured die
  • methanol can be used as a clean burning fuel
  • used as an additive in high performance rating cars
  • extremely toxic and can lead to death
  • it is an important feedstock for the chemical industry and can be converted into methanal and ethanoic acid
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properties of alcohols

  • Hydrogen bonds formed between O-H affect properties

Melting and boiling points

  • High melting and boiling points due to H bonds
  • Have lower volatility than alkanes of a similar mass


  • Can dissolve in water as hydrogen bonds form between the polar O-H groups of the alcohol and water molecules
  • as chain length increases, solubility decreases
  • A large part of the alcohol molecule is the non-polar hydrocarbon chain
  • This does not form hydrogen bonds with water molecules
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Combustion and oxidation of alcohols


  • in lots of oxygen alcohols burn completely to form carbon dioxode and water

Oxidation of Alcohols

  • primary and secondary alcohols can be oxidised using an oxidising agent eg (acidified) potassium dichromate ions
  • during the reaction the potassium dichromate changes colour from orange to green
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primary alcohols

  • Primary alcohols
  • gently heated with pot. dichrom. oxidised to an aldehyde
  • propan-1-ol is oxidised to propanal


  • On stronger heating with excess acidified dichromate the alcohol will be completely oxidised going straight to a carboxylic acid
  • In a lab the aldehyde needs to be distilled off as it is formed, to prevent it being oxidised to a carboxylic acid to make carboxylic acid,the reaction mixture is heated under reflux before distilling off the product.
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Secondary alcohols

Secondary alcohols

  • Secondary alcohols are oxidised further by acidified dichromate ions to produce ketones.
  • Ketomes cannot be oxidised further


  • Tertiary alcohols cannot be oxidised, stays orange.
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  • The reaction of an alcohol with a carboxylic acid to produce an ester and water,sulfuric acid is often used as the catalyst
  • (
  • O-H bond in alcohol is broken and water is formed.
  • Esters-adhesives and solvents. Can produce different fruity smells
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preparing an ester

  • in a boiling tube add 1cm of carboxylic acid to 1cm of the alcohol. Add a few drops of sulfuric acid.
  • place boiling tube in hot water bath (80) for about 5 mins
  • pour the product into a beaker of cold water
  • see an oil floating on the surface of the water. This is the ester
  • Dehydration of an alcohol
  • alcohol is dehydrated to form an alkene (acid catalyst). Elimination reaction
  • alcohol heated under reflux, in the presence of phosphoric acid for 40 mins
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