Hydrogen peroxide, protonated oxygenation

Superoxide ion is not highly reactive towards hydrocarbons (i.e., lipids) and is readily removed from biological systems by superoxide dismutase, forming hydrogen peroxide and oxygen. However, the protonated superoxide ion or hydroperoxyl radical, HO, reacts with NADH and alkanes. Although such a reactive... 

Oxygen Compounds. Although hydrogen peroxide is unreactive toward ozone at room temperature, hydroperoxyl ion reacts rapidly (39). The ozonide ion, after protonation, decomposes to hydroxyl radicals and oxygen. Hydroxyl ions react at a moderate rate with ozone (k = 70). 

The resulting unstable molecular ion Oj) rapidly adds another electron and protons to yield hydrogen peroxide. In alkaline solutions the same pathway is followed, but owing to the much lower polarization, the reaction becomes practically reversible (b = 0.03 V) its rate then is determined by oxygen transport to the surface, and polarization is of the concentration type (Bagotsky and Yablokova, 1953). 

Optical biosensors can be designed when a selective and fast bioreaction produces chemical species that can be determined by an optical sensor. Like the electrochemical sensors, enzymatic reactions that produce oxygen, ammonia, hydrogen peroxide, and protons can be utilized to fabricate optical sensors. 

The product of the one-electron reduction of O2, the superoxide ion, Oi, is highly unstable in acidic-aqueous solutions where its protonated form, the peroxyl radical H02(pA = 4.8), decomposes to ozone, oxygen, and hydrogen peroxide experiments have shown that the two latter compounds are produced almost quantitatively, when only traces of ozone are found. In alkaline solutions, the superoxide ion is more stable even if it decomposes spontaneously to O2 and H02 (AG-6-=—51.13 kj mol ), it has been studied by polarography in NaOH solutions, in the presence of compounds that adsorb at the surface of the electrode and slow down the protonation of 02 . From these electrochemical experiments... 

In the first reaction, the two-electron reduction of molecular oxygen is followed by protonation of the resulting anionic species to yield hydrogen peroxide. On the other hand, the second reaction requires cleavage of the dioxygen bond, followed ultimately by protonation of hydroxide ions to afford water this process has not been observed unless each of the oxygen atoms is able to bind to a unique metal center. 

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