Nitric acid hydroxyl radical reaction

Polyphenols can act as antioxidants by a number of potential pathways. The most important is likely to be by free radical scavenging, in which the polyphenol can break the radical chain reaction. Polyphenols are effective antioxidants in a wide range of chemical oxidation systems, being capable of scavenging peroxyl radicals, alkyl peroxyl radicals, superoxide, hydroxyl radicals, nitric oxide and peroxynitrate in aqueous and organic environments [121]. This activity is due to the ability of donating an H atom from an aromatic hydroxyl group to a free radical, and the major ability of an aromatic structure to support an unpaired electron by delocalization around the 7i-electron system. Phenolic acids... 

Peroxynitrite easily oxidizes nonprotein and protein thiyl groups. In 1991, Radi et al. [102] have shown that peroxynitrite efficiently oxidizes cysteine to its disulfide form and bovine serum albumin (BSA) to some derivative of sulfenic acid supposedly via the decomposition to nitric dioxide and hydroxyl radicals. Pryor et al. [124] suggested that the oxidation of methionine and its analog 2-keto-4-thiomethylbutanic acid occurred by two competing mechanisms, namely, the second-order reaction of sulfide formation and the one-electron... 

It should be noted that Reaction (4) is not a one-stage process.) Both free radical N02 and highly reactive peroxynitrite are the initiators of lipid peroxidation although the elementary stages of initiation by these compounds are not fully understood. (Crow et al. [45] suggested that trans-ONOO is protonated into trans peroxynitrous acid, which is isomerized into the unstable cis form. The latter is easily decomposed to form hydroxyl radical.) Another possible mechanism of prooxidant activity of nitric oxide is the modification of unsaturated fatty acids and lipids through the formation of active nitrated lipid derivatives. 

Brown, S. S., R. K. Talukdar, and A. R. Ravishankara, Reconsideration of the Rate Constant for the Reaction of Hydroxyl Radicals with Nitric Acid, J. Phys. Chem. A 103, 3031-3037 (1999b). 

Fig. 7.3 Reactions showing the generation of ROS during lipid peroxidation and oxidative stress. Hydroxyl radical ( OH) lipid radical ( lipid), peroxyl radical (lipid-OO ) lipid peroxide (lipid-OOH) nitric oxide ( NO) nitrogen dioxide (N02) peroxynitrite anion (ONOO-) hypochlorous acid (HOC1), and hydrogen peroxide (H202)...

In ambient air, the primary removal mechanism for acrolein is predicted to be reaction with photochemically generated hydroxyl radicals (half-life 15-20 hours). Products of this reaction include carbon monoxide, formaldehyde, and glycolaldehyde. In the presence of nitrogen oxides, peroxynitrate and nitric acid are also formed. Small amounts of acrolein may also be removed from the atmosphere in precipitation. Insufficient data are available to predict the fate of acrolein in indoor air. In water, small amounts of acrolein may be removed by volatilization (half-life 23 hours from a model river 1 m deep), aerobic biodegradation, or reversible hydration to 0-hydroxypropionaldehyde, which subsequently biodegrades. Half-lives less than 1-3 days for small amounts of acrolein in surface water have been observed. When highly concentrated amounts of acrolein are released or spilled into water, this compound may polymerize by oxidation or hydration processes. In soil, acrolein is expected to be subject to the same removal processes as in water. 

The atomic oxygen thus produced can react with molecular oxygen to form ozone. Acid rain results from the reaction of NO2 and SO3 with hydroxyl radical and water vapor in the air to form nitric acid (HNO3) and sulfuric acid (H2SO4). The acids dissolve in water and return to the earth in the rain. 

NO2 in the troposphere reacts with hydroxyl radicals (from reaction 8.10, via reactions 8.2, 8.6, and 8.10) to form nitric acid ... 

Nitric acid forms in the atmosphere as a result of the reaction between hydroxyl radicals and NO1 ... 

Peroxynitrite (ONOO ) is a cytotoxic species generated by the reaction between snperoxide and nitric oxide (NO), which is a very strong oxidant and can cause oxidation of cell membrane protein and lead to cell damage and diseases. It can also generate hydroxyl radicals and NO2 nnder acidic conditions. Pannala et al." found that the scavenging effect of ECG and EGCG on ONOO was more pronounced than that of EC and EGC. Catechins were also found to protect from peroxynitrite-... 

The current convention is that, the products of the reactions of atmospheric NOx with organic radicals, hydroxyl radical, and hydroperoxy radical (HO2) are known collectively as NOy. Two of the major NOy species are nitric acid (HNO3) and the PANs (RCO-OO-NO2). Some of the more common PANs are listed in Table 19.1, and the most stable structures for the first three analogs are... 

Reactions of alkanes with hydroxyl radicals, which take place in the atmosphere under the action of irradiation and occur as crucial stages in oxidation of hydrocarbons are of great importance and have been investigated in detail [20], The data for reactions of HO with some alkanes are summarized in Table II.2 [20f], Reaction of alkanes with nitric acid occurs as a radical chain process with participation of radicals HO andN02 [21] ... 

Hydroxyl radical losses occur almost exclusively via reaction with NO2 to form HNO3. Between VOC/NO = 4 and 8 an increase in OH concentration is sufficient to offset the decrease in the amount of NO2 present, causing nitric acid formation to remain relatively constant (77 ppb at VOC/NO, = 4 and 79 ppb at VOC/NO, = 8), but at high VOC/NO,... 

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