5.5.2

Oxidation of Alcohols

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Ketones and Aldehydes

Ketones and aldehydes are functional groups that can be produced by the oxidation of alcohols.

Illustrative background for KetonesIllustrative background for Ketones ?? "content

Ketones

  • When you oxidise a secondary alcohol, the molecule you get is called a ketone.
    • Ketones have a carbon double bonded to an oxygen atom, and two other single carbon-carbon bonds.
    • The simplest ketone, propanone (acetone), is shown here.
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Naming ketones

  • We use the general name:
    • Alkan-X-one:
      • Propanone.
      • Butanone.
      • Pentan-2-one or pentan-3-one.
  • The numbers are used on longer alkanes to show on which carbon the ketone group lies.
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Aldehydes

  • You can oxidise a primary alcohol to an aldehyde.
    • An aldehyde has a carbon-oxygen double bond and at least one carbon-hydrogen bond.
    • The simplest aldehyde, methanal (formaldehyde), is shown here.
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Naming aldehydes

  • We use the general name:
    • Alkanal:
      • Propanal.
      • Butanal.
      • Pentanal.
  • Here, there is no need for any numbers as the aldehyde group must lie on one of the end carbons.
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Carboxylic acids

  • You can oxidise an aldehyde to a carboxylic acid.
    • You cannot oxidise a ketone to a carboxylic acid.
    • The simplest acid, methanoic acid (formic acid), is shown here.

Oxidation of Alcohols

There are different kinds of alcohols, and as always in chemistry, they all have slightly different reactions.

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Oxidation

  • Each of the kinds of alcohol can be oxidised to different extents.
  • The rule is that you can break carbon-hydrogen bonds, but not a carbon-carbon bond.
    • Primary alcohols can be oxidised twice.
    • Secondary alcohols can be oxidised once.
    • Tertiary alcohols cannot be oxidised.
  • The usual oxidising agent, for all, is acidified potassium dichromate(VI).
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Primary alcohols

  • Two possible oxidation reactions for primary alcohols:
    • They can be oxidised to aldehydes.
    • If you change the experimental conditions, you can also oxidise them to carboxylic acids.
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Secondary alcohols

  • One possible oxidation reaction for secondary alcohols:
    • You can oxidise them to a ketone.
      • You cannot oxidise it further without breaking carbon-carbon bonds.
Illustrative background for Tertiary alcoholsIllustrative background for Tertiary alcohols ?? "content

Tertiary alcohols

  • You can’t oxidise a tertiary alcohol at all!
    • Tertiary alcohols have three carbon groups bonded to the alcohol carbon.
    • The only way to add more oxygen involves breaking carbon-carbon bonds.

Jump to other topics

1Physical Chemistry

2Physical Chemistry 2 (A2 Only)

3Inorganic Chemistry

4Inorganic Chemistry 2 (A2 Only)

5Organic Chemistry 1

6Organic Chemistry 2 (A2 Only)

6.1Optical Isomerism (A2 Only)

6.2Aldehydes & Ketones (A2 Only)

6.3Carboxylic Acids & Esters (A2 Only)

6.4Aromatic Chemistry (A2 Only)

6.5Amines (A2 Only)

6.6Polymers (A2 Only)

6.7Biological Organic (A2 Only)

6.8Organic Synthesis (A2 Only)

6.9NMR Spectroscopy (A2 Only)

6.10Chromatography (A2 Only)

6.11A-A* (AO3/4) - Organic 2

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