The aldehydes will react further with (KMnO4), being oxidized to become carboxylic acids. Controlling the temperature and concentration of the reagent can keep the reaction from continuing past the formation of the glycol.
Aldehydes will react further with potassium permanganate (KMnO4), being oxidized to form carboxylic acids. Controlling the temperature and concentration of the reagent can prevent the reaction from proceeding beyond the formation of the glycol.