As the substrate there are conjugated RX systems with the substituent X detached by the cathodic reaction. Among these are, in particular, vitamin A, with all-trans-conjugated system, and cinnamyl-derivatives (Fig. ). For vitamin A, an unusual reaction pathway has been established: the first two-electron stage proceeds with the clea va ge of t he su bst itu ent Х, and only the next two steps touch the pentaenic conjugate system :