An electron spin resonance study of side reactions in the equilibria of formation of triple ions

Reduction of aromatic compounds A (A = nitrobenzene,1,2-dinitrobenzene, 1,3-dinitrobenzene, 1,4-dinitrobenzene, 3-nitropyridine, 3,5-dinitropyridine, 4-nitrobenzophenone, 4,4′-dinitrobenzophenone, benzonitrile, 1,2-dicyanobenzene, 1,3-dicyanobenzene, 1,4-dicyanobenzene, and 4,4′-dicyanobenzophenone) by alkali metals in ethereal solvents containing sodium tetraphenylborate, yields ion pairs A–˙Na+, which are in equilibrium with the corresponding triple ions Na+A–˙Na+. In a few cases side reactions in the formation equilibria of triple ions are observed by e.s.r. spectroscopy. The decomposition of sodium tetraphenylborate is ascertained and the formation of biphenyl and p-benzosemiquinone is explained as dependent on the number and the position of the substituents in the radical anion A–˙.