In a plentiful supply of oxygen, alcohols burn to form carbon dioxide and water.
Primary and secondary alcohols can be oxidised using an oxidising agent. A suitable oxidising agent is a solution containing acidified dichromate ions (H+, Cr2O72-). This oxidising mixture can be made from potassium dichromate (K2Cr2O7) and sulfuric acid (H2SO4). During the reaction, the acified potassium dichromate changes colour from orange to green.
Primary Alcohols
On gentle heating with acidified potassium dichromate, a primary alcohol can be oxidised to produce an aldehyde.
On stronger heating with excess acidified dichromate the alcohol will be completely oxidised, passing through the aldehyde stage to form a carboxylic acid.
When preparing aldehydes, you need to distill the aldehydes as it is formed to avoid them being oxidised thurther to form a carboxylic acid. When making a carboxylic acid, the reaction mixture is usually heated under reflux before distilling off the product.
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