Chemistry Organic Compounds

Alcohols, Aldehydes, Carboxylic Acids, Ketones, Esters Halogenoalkanes and CFCs

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Alcohols

  • Functional group: CnH2n+1OH
  • Colourless, flammable liquids
  • Made by the hydration of ethene in presence of phosphoric acid catalyst, temperature of 300C and pressure of 60 atm
    • ethene + water --> ethanol
  • or made by the anaerobic fermentation of glucose, catalysed by the enzyme zymase, found in yeast, at a temperature of 37C. An ethanol concentration of <14% can be produced, but at concentrations >14% the alcohol denatures the enzyme. Higher concentrations are produced by distillation.
    • glucose --> ethanol + carbon dioxide
  • Primary alcohols have 0 or 1 alkyl group bonded to the carbon atom with the OH group attached
  • Secondary alcohols have 2 alkyl groups bonded to the carbon atom with the OH group attached
  • Tertiary alcohols have 3 alkyl groups bonded to the carbon atom with the OH group attached
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Oxidation of Alcohols

  • Partial Oxidation of Primary Alcohols to form aldehydes
    • Ethanol + [O] --> ethanal
    • the ethanol and oxidising agent is heated and the product is distilled off as it forms
    • the oxidising agents are sodium dichromate (V) and concentrated sulphuric acid
    • the oxidising agent is reduced, and changes from orange to colourless
  • Complete Oxidation of Primary Alcohols to form carboxylic acids
    • Ethanol + [O] --> ethanoic acid
    • The ethanal and oxidising agent is heated under reflux conditions
      • reflux is continuous evaporation and condensing of volatile reactants, so they are kept in contact for longer to speed up the reaction
    • The oxidising agents are sodium dichromate (V) and concentrated sulphuric acid
    • the oxidising agent is reduced, and changes from orange to green.
  • Secondary alcohols oxidise once to form ketones
    • Propan-2-ol + [O] --> Propanone + water
    • The reactants are oxidised with sodium dichromate (V) and concentrated sulphuric acid
  • Tertiary alcohols do not oxidise
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Aldehydes

Aldehydes:

  • Contain the functional group of a carbon bonded to a hydrogen atom and double bonded to an oxygen atom
  • e.g. Propanal: C2H5CHO
  • Formed from the partial oxidation of primary alcohols

Carboxylic Acids:

  • Contain the functional group of a carbon bonded to an oxygen bonded to a hydrogen and the same carbon double bonded to an oxygen
  • e.g. Propanoic Acid:C2H5COOH
  • Formed from the complete oxidation of primary alcohol

Ketones:

  • Contain the functional group CH2C=OCH3
  • e.g. propanone
  • Formed from the oxidation of a secondary alcohol
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Esters:

  • Contain the functional group CH2OC=OCH2
  • e.g. methly salicylate and ethyl ethanoate
  • Formed from alcohol + carboxylic acid --> ester
  • CH3OH + C6H4OHCOOH --> C6H4(HO)COOCH3 + H2O
    • the oxygen is removed from the carboxylic acid
  • Esters are often aromatic
  • Esters are named by: alcohol(-anol)yl carboxylic acid(-oic)oate
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Halogenoalkanes and CFCs

Halogenoalkanes:

  • made from alkanes by radical substitution
  • the reactivity of the halogenoalkane increases as you move down the halogen group
  • Halogenoalkanes can be polymerise
  • Thomas Midegeley developed CFCs in the late 1800s

CFCs:

  • Low in reactivity and volatility and non toxic
  • so they were used extensively in aerosols, refrigerants and in air con units
  • Carbon-halogen bonds are very strong
  • CFCs do not break down until they reach the stratosphere where UV radiation from the sun causes the bonds to break and Chlorine radicals to form:
    • -Cl + Ozone --> ClO- + oxygen
    • ClO- + atomic oxygen --> -Cl + oxygen
    • Overall : Ozone + atomic oxygen --> 2 oxygen molecules
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  • This causes ozone depletion, leading to holes in the ozone layer.
  • Allowing harmful UV radiation to reach the lower atmosphere, increasing the prevalence of skin cancers.
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