Oxidation of alcohols

Alcohols can be oxidised using potassum dichromate(vi) acidified with dilute sulphuric acid as the oxidising agent. Learn this name in full and do not short cut bu calling it dichromate or acidified dichromate.

• Primary alcohols are oxidised gently (using warming and distillation at temperature of less than 50C) to aldehydes and more vigorously (boil under reflux) to carboxylic acids.
• Secondary alcohols are oxidised vigorously (by boiling under reflux) to ketones
• Tertiary alcohols are resitant to oxidation (don’t say cannot be oxidised- they can, to CO2 and H2O on combustion!)

Note that for oxidation to occur, the acohol must lose its H attached to the -OH group and also a H on the carbon atom on which the -OH sits. Since tertiary alcohols do not have this H-atom, they are resistant to oxidation.

When attempting equations using structural formula, a [O] is acceptable so. Notes notice that the two H atoms that are removed join with the [O] to form water.:

Primary to an aldehyde

CH3-CH2-CH2-OH + [O] –> CH2-CH2-CHO + H2O

Primary to a carboxylic acid

CH3-CH2 -CH2-OH + 2[O] –> CH2-CH2-COOH + H2O

Secondary to a ketone

CH3-CH(OH)-CH3 + [O} –> CH3-CO-CH3