In  radical disproportionation reactions one molecule acts as an acceptor while the other molecule acts as a donor. In the most common disproportionation reactions, a hydrogen atom is taken, or abstracted by the acceptor as the donor molecule undergoes an elimination reaction to form a double bond. Other atoms such as halogens may also be abstracted during a disproportionation reaction. Abstraction occurs as a head to tail reaction with the atom that is being abstracted facing the radical atom on the other molecule.