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. 2 7 2 2 7 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 further! • 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.