Magnetic field effect on the oxidation of organic substances by molecular oxygen

Magnetic field effect (ME) on certain steps of chain oxidation of organic compounds of different series by molecular oxygen in liquid phase (initiation, chain propagation, and termination) is presented as a function of [O-2] in two regimes. At low concentration of oxygen (<1.5 mM), magnetic field accelerates oxidation by 10% to 100%, but at high concentration no magnetic effect is detected. The dominating contribution into the magnetic effect (ME) is provided by reaction of alkyl radicals to oxygen: R-center dot + O-2 -> RO2 center dot. This reaction is stimulated by the Zeeman interaction which transforms in the encounter pair (R-center dot O-2) producing transformation of quartet spin state, which is spin forbidden to react, into the doublet spin state, which is spin allowed. At high concentration of oxygen, this reaction is not a limiting step and provides no magnetic effect on the total rate of oxidation.