AS Chemistry A OCR - Alcohols

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  • Created by: Shipreck
  • Created on: 11-02-16 17:48

Properties of Alcohols

  • Something is a alcohol when there is one or more hydrogens replaced by the OH functional group.
  • Alcohols are polar as Oxygen has a higher electronegativeity than carbon and hydrogen.
    • This is also due to the hydrogen bonding.
  • Alcohols have hydrogen bonding.
    • Hydrogen bonding occurs between molecules where you have a hydrogen atom attached to one of the very electronegative elements - fluorine, oxygen or nitrogen.
    • Alcohols have a higher boiling point than their comparative alkane. 
    • Alcohols are soluble in water, however, solubility falls as the length of the hydrocarbon chain in the alcohol increases because the OH functional group increasingly donates less to the overall character of the molecule.
    • Alcohols are less volatile than alkanes because the hydrogen bonding needs to be disrupted for the liquid to vaporize.
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Properties of Alcohols Cont.

  • Alcohols are seperated into Primary, Secondary and tertiary. 
    • Primary - the carbon the alcohol is attatched too is connected to one other carbon.
    • Secondary- the carbon the alcohol is attatched too is connected to two other carbons.
    • Tertiary the carbon the alcohol is attatched too is attatched to three other carbons.
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Combustion of Alcohol

  • The more carbon atoms in the Alcohol, the more energy released. But the more oxygen needed.
  • Complete Combustion
    • Products are CO2 and H2O
  • Incomplete Combustion
    • Products are CO/C and H2O.
    • Happens when there is a lack of oxygen.
  • CO is deadly as it binds with the blood in place of Oxygen.
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Oxidation of Alcohol

  • Oxidation is done with hydrogen ions and dichromate ions. (Cr2O7 2–/H+)  
  • Acidified dichromate ions when used in equations is just [O]
  • Oxidation of primary alcohols
    • To create an aldehyde from an alcohol you need 1 [O]. Use distillation conditions.
    •  To create a carboxylic acid you need 2 [O]. Use reflux conditions.
  • Oxidation of secondary alcohols.
    • To create a ketone you need 1 [O]. Use reflux conditions.
  • Tertiary alcohols are resistant to oxidation.
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Elimination of H2O in alcohol

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Elimination of H2O in alcohol

  • Reagents
    • Alcohol
  • Conditions
    • Acid catalyst (e.g. H3PO4 or H2SO4) and heat
  • Products
    • Alkene
  • Cannot happen if the carbon attatched to the carbon with the OH group is tertiary, as that is where the other H comes from to form H2O.
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Substitution with Halide

  • The Halogen ion swaps with the OH group, creating a halogenoalkane.


  • Conditions: The presence of acid (e.g. NaBr/H2SO4) 
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