The determination of the oxygen consumption in autoxidation studies by means of EPR spectroscopy

Stable paramagnetic species give rise in the presence of oxygen to EPR spectra characterized by broad lines due to Heisenberg spin exchange. This property can be conveniently used to determine the amount of oxygen present in the system under investigation. In the present paper we describe the use for this purpose of two radical probes: one is the stable aliphatic nitroxide 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) which is employed as a homogeneous probe and the other is fusinite, a derivative of coal used as a finely grinded black powder totally insoluble both in water and in organic solvents. Both have been employed to follow the autoxidation reaction of three representative oxidizable substrates, i.e. cumene, styrene and methyl linoleate, in solution of chlorobenzene or of tert-butyl alcohol. The advantages of this technique with respect to traditional methods are emphasized.