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Oxidation of Alcohols

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

Oxidation

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(V).
Primary alcohols

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.
Secondary alcohols

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.
Tertiary alcohols

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.

Ketones and Aldehydes

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

Ketones

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.
Naming ketones

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.
Aldehydes

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.
Naming aldehydes

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.
Carboxylic acids

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.
Jump to other topics
1

Physical Chemistry

1.1

Atoms, Molecules & Stoichiometry

1.2

Atomic Structure

1.3

Chemical Bonding

1.4

States of Matter

1.5

Chemical Energetics

1.6

Electrochemistry

1.7

Equilibria

1.8

Partition Coefficient

1.9

Reaction Kinetics

2

Inorganic Chemistry

3

Organic Chemistry & Analysis

3.1

Introduction to Organic Chemistry

3.2

Hydrocarbons

3.3

Halogen Derivatives

3.4

Hydroxy Compounds

3.5

Carbonyl Compounds

3.6

Carboxylic Acids & Derivatives

3.7

Nitrogen Compounds

3.8

Polymerisation

3.9

Analytical Techniques

3.10

Organic Synthesis

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