Fotografia do Projeto Capela da Ciência Selecionada para a Seção Chemistry in Pictures da Revista C&EN (Chemical and Engineering News)
The reaction procedure shown in the photo is as follows: 50 mL of concentrated H2SO4 are added to a beaker, then the same volume of ethanol is added. The ethanol slowly diffuses into the acid as it is less dense than H2SO4. At the time of formation of two visible liquid phases (ethanol/H2SO4), 500 mg of potassium permanganate is added and the formation of sparks is observed at the ethanol/H2SO4 interface. These sparks originate from the exothermic oxidation of ethanol with potassium permanganate in the presence of concentrated sulfuric acid.
In ethanol, the hydroxyl carbon is bonded to only one carbon atom, that is, the two other ligands are hydrogen, with two places for the nascent oxygen to attack: initially, there will be the formation of an aldehyde (acetaldehyde), then the continuous oxidation, and other nascent oxygen attacks the carbonyl carbon and produces a carboxylic acid (acetic acid), according to the reaction:
Note: The reaction between potassium permanganate and sulfuric acid produces a greenish sludge-like liquid that is a mixture of potassium sulphate (K2SO4), water (H2O) and dimanganese heptoxide (Mn2O7). The heptoxide, when it comes in contact with any organic material (ethanol), promotes a violent combustion reaction.
This reaction and others are connected with Chemistry teaching activities and scientific dissemination realized on the Science Chapel project. The goal of the Science Chapel project is to develop engaging demonstrations for high school students.
