Electron-transfer processes in the reaction of K−, K+(15-crown-5)2 with carbazole: unexpected formation of metallic potassium

Transfer of one electron from K− to the aromatic ring occurs in the reaction of K−, K+(15-crown-5)2 with carbazole giving K° and a radical anion. The latter rapidly decomposes with the liberation of hydrogen and formation of carbazylpotassium. It can also undergo an intramolecular proton-exchange reaction followed by a transfer of the second electron from the part of K° product. That leads to a dianion which then reacts with another carbazole molecule. Finally, carbazylpotassium and 1,4-dihydrocarbazylpotassium are formed.