Oxidation of Alcohols

Oxidation of Alcohols
By Iona and Catherine
Oxidising Agents
• Primary and secondary alcohols can be oxidised
using an oxidising agent, notated by [o].
• A suitable oxidising agent is a solution
containing acidified dichromate ions (H+ and
Cr O 2-).
• These ions come from a mixture of K Cr O and
sulphuric acid.
• During the reaction there will be a colour change
of orange to green.
Primary Alcohol
• With gentle heating, a primary alcohol
can be oxidised to produce an aldehyde.
• With strong heating and excess [o] a
carboxylic acid is formed.
• Reflux apparatus is generally used to
produce carboxylic acids.
• Aldehydes must be distilled as they are
formed to prevent further oxidation which
may form carboxylic acids.
Aldehydes have a C=O bond at the end of a carbon chain
Carboxylic acids have a C=O and C-OH group.
Secondary Alcohols
• Secondary alcohols are oxidised to
produce ketones, they cannot be oxidised
• Secondary alcohols are oxidised with
gentle heat and the same oxidising agent.
• Ketones have a C=O bond in the middle of
a carbon chain.
Tertiary Alcohols
• These are resistant to oxidation, there will
be no colour change.
• This is because the carbon which the
alcohol group is bonded to is not bonded
to any other hydrogen atoms and so no
double bonds can be created.