By atom manipulation we performed on-surface chemical reactions of a single molecule on a multilayer insulating film using noncontact atomic force microscopy. The single-electron sensitivity of atomic force microscopy allows us to follow the addition of single electrons to the molecule and the investigation of the reaction products. By performing a novel strategy based on long-lived doubly charged states a single molecule is fragmented. The fragmentation can be reverted by again changing the charge state of the system, characterizing a reversible reaction. The experimental results in addition to density-functional theory provide insight into the charge states of the different products and reaction pathways. Similar molecular systems could be used as charge-transfer units and to induce reversible chemical reactions.