Iodide ion promotes the free radical addition of t-BuHgI to acrylonitrile to form t-BuCH(2)CH(CN)HgI. A facile reaction of the adduct 1-cyanoalkyl radical with t-BuHgI(2)(-) is indicated. Further promotion is observed in the presence of NH4I or PTSA/KI in a reaction now leading directly to t-BuCH(2)CH(2)CN. Protonation of the intermediate adduct radical followed by electron transfer from t-BuHgI(2)(-) is postulated. With fumaronitrile reaction of the adduct, radical [t-BuCH(CN)(CHCN)-H-.] with t-BuHgI can be promoted by the addition of acids or bases. In the presence of NH4I or PTSA/KI, the reductive alkylation product is formed, while in the presence of DABCO, oxidative alkylation occurs to yield t-BuC(CN)=CHCN and t-BuC(CN)=C(CN)Bu-t. Protonation of [t-BuCH(CN)(CHCN)-H-.] increases the ease of reduction while deprotonation yields an easily oxidized radical anion.