Oxidation of Alcohols

Alcohols can be oxidised by acidified potassium dichromate(VI): potassium dichromate(VI), K₂Cr₂O₇, with dilute sulfuric acid.When the alcohol is oxidised, the orange dichromate(VI) ions are reduced to green chromium(III) ions:Cr₂O₇²⁻ (orange) → Cr³⁺ (green)This colour change shows that oxidation has taken place.In equations the oxidising agent is written as [O], which stands for an oxygen atom from the oxidising agent. The equation must still balance. Oxidation removes two hydrogen atoms: one from the -OH group and one from the carbon bonded to it. These combine with [O] to form water.What an alcohol forms depends on its class:
Primary alcohols are oxidised to aldehydes, which can be oxidised further to carboxylic acids.
Secondary alcohols are oxidised to ketones.
Tertiary alcohols are not easily oxidised, because the C-OH carbon has no hydrogen atom to lose. The dichromate stays orange.Worked example: write the equation for the oxidation of propan-2-ol.
Propan-2-ol, CH₃CH(OH)CH₃, loses 2 H atoms, which join [O] to form H₂O:CH₃CH(OH)CH₃ + [O] → CH₃COCH₃ + H₂OThe product is propanone, a ketone.The colour change can therefore be used to tell tertiary alcohols apart from primary and secondary alcohols.