Nitrate, photochemical reactions with

Nitrogen oxides other than nitrogen dioxide have been studied for possible adverse health effects. Chemical analysis of ambient aerosols collected in southern California has revealed that nitrates exhibit particularly high values compared to other parts of the United States. These aerosols are generally acidic in nature and are composed of nitric acid and nitrate salts that are formed through photochemical reactions with nitrogen dioxide and other oxides of... 

This work was intended to give information about non-photochemical processes affecting species that are involved in hydrocarbon oxidation and ozone formation, such as the hydrocarbons themselves or the active nitrogen compounds. The main part of the work was concerned with rates and products in nitrate radical reactions with various hydrocarbons. Some interest was also taken in purely inorganic reactions. 

Some work [5] has been performed on the photochemical reaction between sulfur dioxide and hydrocarbons, both paraffins and olefins. In all cases, mists were found, and these mists settled out in the reaction vessels as oils with the characteristics of sulfuric acids. Because of the small amounts of materials formed, great problems arise in elucidating particular steps. When NO and 02 are added to this system, the situation is most complex. Bulfalini [3] sums up the status in this way The aerosol formed from mixtures of the lower hydrocarbons with NO and S02 is predominantly sulfuric acid, whereas the higher olefin hydrocarbons appear to produce carbonaceous aerosols also, possibly organic acids, sulfonic or sulfuric acids, nitrate-esters, etc. ... 

Peroxyacetyl nitrate (PAN), H3CCO2ONO2, is a constituent of photochemical smog. It undergoes a first-order decomposition reaction with fi/2 = 32 min. 

Chemical radicals—such as hydroxyl, peroxyhydroxyl, and various alkyl and aryl species—have either been observed in laboratory studies or have been postulated as photochemical reaction intermediates. Atmospheric photochemical reactions also result in the formation of finely divided suspended particles (secondary aerosols), which create atmospheric haze. Their chemical content is enriched with sulfates (from sulfur dioxide), nitrates (from nitrogen dioxide, nitric oxide, and peroxyacylnitrates), ammonium (from ammonia), chloride (from sea salt), water, and oxygenated, sulfiirated, and nitrated organic compounds (from chemical combination of ozone and oxygen with hydrocarbon, sulfur oxide, and nitrogen oxide fragments). ... 

Dinitrogen pentoxide reacts with alkanes in carbon tetrachloride at 0 °C via a radical mechanism to give nitration products which can include nitrate esters.Reactions of alkanes with dinitrogen pentoxide in nitric acid are complex and of little synthetic value. 1-Adamantyl nitrate is one of the products obtained from the photochemical irradiation of a solution of adamantane and dinitrogen pentoxide in methylene chloride. ... 

Another debatable approach to pollution control involves the methods currently used to reduce hydrocarbons and CO in automotive exhausts. The need to control CO is based on its direct health effects while the need to control the hydrocarbons is based on their interactions with the N02 photolytic cycle which leads to elevated concentrations of N02, 03, peroxyacyl nitrates, and aerosols. The solution adopted was to increase the efficiency of the combustion process, thereby reducing hydrocarbon and CO emissions. Unfortunately, the method adopted also leads to dramatic increases in NO emissions. When this increase in NO was objected to, the answer came back that increased NO in the atmosphere is beneficial since it rapidly reacts with and destroys ozone, one of the very health-related substances requiring control. This is another example of failure to view the total air pollution system. Of course NO destroys 03, but one product of this reaction is N02 which is also detrimental to health. Furthermore, this N02 is the beginning point of sunlight absorption which leads to all the products of photochemical interactions. In a certain location excess NO will tend to reduce 03 levels. However, downstream of these locations excess N02 will promote more photochemical reactions and perhaps even higher ozone levels. In part this nonsolution to automotive pollution may be a major cause of the substantial increases in ozone in many areas during the past few years. This automotive example clearly illustrates the need for in-depth analysis when plans are made to change any part of the system of air pollution. Decisions based on such an analysis are all the more important because the tradeoffs involve human health and welfare. 

Peroxynitrous acid, ONOOH, forms in another photochemical channel at shorter wavelengths but is absent at k > 300 nm. The O-atoms generated in reaction 99 may react with 02([02 Water 0.3 mM) via reaction 100 or, preferably, with nitrate via reaction 101. Nitrite (smax = 22.5 M 1 cm1 at 360 nm) will undergo secondary photolysis, reaction 102, and oxidation by OH radicals, reaction 103 ... 

The irradiation of nitrate in the presence of 2-phenylphenol yields oxidation (phenylhydroquinone, phenylbenzoquinone, 2-hydroxydibenzofuran) and nitration intermediates (2-hydroxy-3-nitrobiphenyl and 2-hydroxy-5-nitrobiphenyl) [124]. 2-Hydroxydibenzofuran is formed by photocyclisation of phenylbenzoquinone. Nitration might be due to reaction with nitrogen dioxide, but an interesting aspect is the effect of pH. The fact that nitration is favoured at low pH might indicate a role of photoformed nitrous acid, due to either photochemical or dark reactivity [124], It is worth noting that the... 

Sodium oxalate has been used as a primary standard substance for Ce(IV) in sulfuric acid. In the absence of a catalyst a temperature of 70 to 75°C is necessary. Smith and Getz found that in 1 to 2 M perchloric acid solution, sodium oxalate can be titrated at room temperature with Ce(IV) perchlorate or nitrate but not with sulfate. Rao, Rao, and Rao carried out the titration at room temperature in the presence of barium chloride to remove sulfate, which retards the reaction between oxalate and Ce(IV) and between oxalate and oxidized ferroin. Alternatively, some Fe(III) was added, and the trace of Fe(II) produced photochemically then reacted with the indicator. Rao, Rao, and Murty carried out the titration in 0.5 M HNOj with ammonium hexanitratocerate(IV) instead of the sulfate. With a small amount of KI and KIO3, a satisfactory end point was obtained at room temperature with ferroin as indicator. 

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