Redox systems hydroxylamine

This kind of redox system leads also to other free-radical species and the obtained polymers are not purely hydroxytelechelic. Hydroxylamine/mineral acid (HC1, H2S04)/H202 55 59,60), NaHS03/H202 55), ascorbic acid/H202 61), thiourea (or N-substituted thiourea)/H202 62 -64) systems have been suggested. The last one yields mostly hydroxyl-terminated polymers. 

The polymerization of calcium acrylate may be initiated with typical redox systems such as ammonium persulfate-sodium thiosulfate and certain peroxides with reducing agents such as sodium thiosulfate. Hydroxylamine hydrochloride, hydrazine hydrate, and tetramethylenepentamine are also suitable reducing agents with certain oxidizing agents [110]. 

To undertake oxidation of both cyclic and acyclic hydroxylamines to nitrones, an electrochemical oxidative system has been developed, where WC>42-/WC>52-are used as cathodic redox mediators and Br /Br2 or I—/I2 as anodic redox mediators (129-131). 

Tertiary amine oxides and hydroxy la mines are also reduced by cytochromes P-450. Hydroxylamines, as well as being reduced by cytochromes P-450, are also reduced by a flavoprotein, which is part of a system, which requires NADH and includes NADH cytochrome b5 reductase and cytochrome b5. Quinones, such as the anticancer drug adriamycin (doxorubicin) and menadione, can undergo one-electron reduction catalyzed by NADPH cytochrome P-450 reductase. The semiquinone product may be oxidized back to the quinone with the concomitant production of superoxide anion radical, giving rise to redox cycling and potential cytotoxicity. This underlies the cardiac toxicity of adriamycin (see chap. 6). 

Cerium (III) or tin(II) ions were chosen as a reductant [5]. Application of redox processes is promising for the synthesis of novel sarcophaginates with higher stability and a small cavity size. The reactivity of sarcophaginate ligands may also be employed to prepare imine-, hydroxylamine-, and amide-containing systems not only with cyclohexanediamine derivatives, but with simpler clathrochelates as well. 

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