**1. Introduction**

262 Nitroxides – Theory, Experiment and Applications

*J Org Chem* 71, 6044-6052.

Zubenko, D.;Tsentalovich, Y.;Lebedeva, N.;Kirilyuk, I.;Roshchupkina, G.;Zhurko, I.;Reznikov, V.;Marque, S.R.A. & Bagryanskaya, E. (2006). Laser Flash Photolysis and CIDNP Studies of Steric Effects on Coupling Rate Constants of Imidazolidine Nitroxide with Carbon-Centered Radicals, Methyl Isobutyrate-2-yl and tert-Butyl Propionate-2-yl.

> Stable nitroxide radicals (>NO•) play very important role in experimental studies and in theoretical analysis of chemical and biochemical processes' mechanism for over 50 years.

> For a long time it was believed that cyclic stable nitroxide radicals (piperidine, pyrroline, and imidazoline >NO•) inhibit oxidation of hydrocarbons (RH) and 1- and 1,1- ethylene substituted monomers (M) only via reaction with substrate's alkyl radicals in accordance with Scheme 1 (Buchachenko, 1965; Denisov & Afanas'ev, 2005; Mogilevich & Pliss, 1990). If substrate is M then chains are propagated by polyperoxide radicals (MO2•) through its addition to monomer's double bond in accordance with the reaction: MO2• + M M• (Mogilevich & Pliss, 1990).


**Scheme 1.** Classical mechanism of organic compounds oxidation inhibited by nitroxide radicals

At the same time a probability of direct reaction of nitroxide with peroxide radicals is considered in a number of works (Barton, 1998; Goldstein & Samuni, 2007; Offer & Samuni, 2002; Pliss et al., 2010a, 2010b, 2012). Therefore it is necessary to review the most significant results in the field of kinetics and mechanism of elementary reactions of piperidine,

© 2012 Pliss et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 Pliss et al.,licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

pyrroline, and imidazoline >NO• with active particles of chemical and biochemical oxidation processes. Such an attempt has been made in this review.

Structures of nitroxide radicals and corresponding hydroxylamines which reactions' mechanisms were analyzed in this work are presented in Figure 1.

**Figure 1.** Structures of nitroxide radicals and corresponding hydroxylamines
