Nitro compounds radiolysis

IV. RADIOLYSIS OF NITRO AND NITROSO COMPOUNDS A. Aliphatic Nitro Compounds... 

Aromatic nitro compounds are also prone to undergo one-electron reduction on pulse radiolysis. The behaviour of the radical cation so formed is dependent upon the type of... 

Wardman P, Dennis MF, Everett SA, Patel KB, Stratford MRL, Tracy M (2003) Radicals from one-electron reduction of nitro compounds, aromatic N-oxides and quinones the kinetic basis for hypoxia-selective, bioreductive drugs. Biochem Soc Symp 61 171-194 Warman JM, de Haas MP, Hummel A, van Lith D, VerberneJB, Loman H (1980) A pulse radiolysis conductivity study of frozen aqueous solutions of DNA. Int J Radiat Biol 38 459-459 Warman JM, de Haas MP, Rupprecht A (1996) DNA a molecular wire Chem Phys Lett 249 319-322 Warters RL, Lyons BW (1992) Variation in radiation-induced formation of DNA double-strand breaks as a function of chromatin structure. Radiat Res 130 309-318 Warters RL, Hofer KG, Harris CR, Smith JM (1977) Radionuclide toxicity in cultured mammalian cells Elucidation of the primary site of radiation damage. Curr Top Radiat Res Q 12 389-407 Weiland B, Huttermann J (1998) Free radicals from X-irradiated, dry and hydrated lyophilized DNA as studies by electron spin resonance spectroscopy analysis of spectral components between 77 K and room temperature. Int J Radiat Biol 74 341-358 Weinfeld M, Soderlind K-JM (1991) 32P-Postlabeling detection of radiation-induced DNA-damage identification and estimation of thymine glycols and phosphoglycolate termini. Biochemistry 30 1091-1097... 

Aliphatic nitro compounds are characterized by another interesting and mechanistically important property. Based on tautomeric and protolytic equilibria the stable form of nitromethane in basic solution is that of a double bonded ac/-nitromethane anion, CH2=N02 , which becomes ready target for electrophilic radical additions. An example, studied by pulse radiolysis, is its reaction with hydroxyl radicals as formulated in eq. 3."... 

Several studies have reported the influence of nitroimidazole derivatives on biological systems. Thus the influence of Misonidazole, l-(2-nitro-l-imidazoyl)-3-methoxy-propan-2-ol, on strand breaking in calf thymus DNA under ionizing radiation conditions has been assessed70. Pulse-radiolysis studies of nitroheterocyclic compounds have examined... 

Effect of the Atmosphere. The composition of radiolysis products depends substantially on the degree of saturation of the irradiated system with oxygen. In a nitrogen atmosphere, the major radiolysis products of the system TBP-diluent-HN03 were alkyl-nitro and -nitrate compounds. However, in the presence of oxygen, the yields of these compounds were sharply reduced, and an accumulation of carbonyl compounds was measured (11, 25). 

The first topic to be dealt with in this article dates back to the early days of pulse radiolysis and is concerned with intermediates generated from organic nitro and nitroso compounds in some elementary redox processes. This will be followed by a presentation of some most recent results on aminyl radicals derived from amino acids, exemplifying the diversity of possible reactions of a seemingly simple type of radicals. The third example on aniline and aniline radicals aims to demonstrate the potential of time-resolved resonance Raman spectroscopy. A common message of all these studies on N-centered radicals hints at the importance of acid/base properties of radicals. The aniline system, in particular, also draws attention to spin and charge distribution, and possible implications to the chemistry of radical species. 

Thus, the calculations [13] have produced evidence in favor of the Kornblum-Russell mechanism elucidating certain details of the nature and structural conditions for realization of its individual steps. Of course, so far only the simplest models have been considered, and the effect of the simplifying assumptions may in some cases be quite substantial. For example, experimental studies of radical-anions of various halogennitrobenzyl compounds IV using the impulse radiolysis technique [28] show that, unlike the chloronitromethyl radical considered earlier, the compounds IV do exist in solution for some finite time. Even so, their decomposition is, in accordance with the theoretical prediction, speeded up upon weakening of the C—X bond. The reaction proceeds by the scheme of intramolecular, inner-sphere electron transfer whose relatively low rate constant (10 -10 s) can be accounted for by the small overlap of the Ti-orbital, which carries the unpaired electron in the initial form IV and is localized predominantly at the nitro group, and the (j -orbital C—X ... 

---