EPR study of radicals formed from aliphatic nitriles

Abstract

By using the TiCl 3H 2O 2 radical-generating method within a continuous-flow system at 25 ± 2°C, a comprehensive EPR study of twelve substrates, acetonitrile, propionitrile, butyronitrile, trimethylacetonitrile, succinonitrile, adiponitrile, glycolonitrile, lactonitrile, 2-hydroxyisobutyronitrile, cyanoacetic acid, methyl cyanoacetate, and ethyl cyanoacetate, has been carried out. For each substrate except the two cyanoacetates, it was generally possible to characterize the spectrum of every radical that could conceivably be formed by hydrogen-atom abstraction from carbon. For methyl and ethyl cyanoactate, respectively, the absorption observed was consistent with the presence of more than one radical, but only the spectrum of ·CH 2OOCCH 2CN and ·CH 2CH 2OOCCH 2CN could be characterized. With the use of their H 2O 2 photo-flow method, R. Livingston and H. Zeldes have investigated as substrates some of the nitriles included in this present study, in most cases using non-aqueous solvents. For each substrate, only the α-CN radical, formed by hydrogen-atom abstraction from the C-2 position, could be characterized. Consequently, the results of the present study complement and considerably extend those from their investigation.