Acetone (1) is a naturally occuring prodcut of the cellular intermediary metabolism. Besides elimination from mammalian organism by the lungs acetone (1) may be oxidized to hydroxyacetone (2) and dihydroxyacetone (3), and further oxidized to lactic acid, which is integrated into the glucose metabolism. A reversible recution to 2-propanol (4) by alcohol dehydrogenase is alos possible.