In the preparation of aldehydes from primary alcohols, aldehydes formed must be distilled as soon as they are formed. Why ?

Explanation

Aldehydes formed as a result of the oxidation of primary alcohols are prone to further oxidation and are expected to form acids. Therefore, it is advisable to remove them form the reaction mixture by distillation. Otherwise other methods must be used to convert primary alcohols into aldehydes such as use an excess of the alcohol. That means that there isn't enough oxidizing agent present to carry out the second stage and oxidize the aldehyde formed to a carboxylic acid.