Investigation of the reaction of 1,2,3-trimethyl-2-phenylbenzimidazoline with dehydrogenating reagents by EPR spectroscopy

The reaction of 1,2,3-trimethyl-2-phenylbenzimidazoline with a number of reagents that manifest dehydrogenating properties with respect to benzimidazolines was studied by EPR spectroscopy. These reagents convert 1,2,3-trimethyl-2-phenylbenzimidazoline to a relatively stable cation radical. The mechanism of the dehydrogenation of benzimidazolines is discussed taking into account the established facts. The values of the hyperfine coupling (HFC) constants provide evidence that the highest occupied molecular orbital (HOMO) of the cation radical is similar in character to the antisymmetric e/sub 1/ orbital of benzene; the nodal points are the 4 and 7 positions of the benzimidazoline, in which the density of the unpaired electron is equal or close to zero.