Nitrous Oxide, NO

Upon the irradiation the nitrous acid ester 1 decomposes to give nitrous oxide (NO) and an alkoxy radical species 3. The latter further reacts by an intramolecular hydrogen abstraction via a cyclic, six-membered transition state 4 to give an intermediate carbon radical species 5, which then reacts with the nitrous oxide to yield the 3-nitroso alcohol 2 ... 

FIGURE 7.8 NOx control in combustion by reburning. Addition of hydroearbons (CHn) late in the eombustion process leads to the reduetion of nitrous oxide (NO) to nitrogen gas (N2). 

The actual mechanism by which the N=N molecule cleaves is very complicated, and is not fully understood yet. It is nevertheless clear that much nitrogen is oxidized to form nitrous oxide, NO. This NO dissolves in the water that inevitably accompanies lightning and forms water-soluble nitrous acid HNO2, which further oxidizes during the storm to form nitric acid, HNO3. Nitric acid functions as a high-quality fertilizer. It has been estimated that a thunderstorm can yield many tonnes of fertilizer per acre of land. 

Recent emission control system development in the automotive industry has been directed mainly towards the use of three-way or dual bed catalytic converters, This type of converter system not only oxidizes the hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas but will also reduce the nitrous oxides (NO ). An integral part of this type of system is the exhaust oxygen sensor which is used to provide feedback for closed loop control of the air-fuel ratio. This is necessary since this type of catalytic converter system operates efficiently only when the composition of the exhaust gas is very near the stoichiometric point. 

A burning dump emits 5 g/s of nitrous oxide (NO), spread over 50 m x 50 m, with an initial cloud height of 3 m. Estimate the maximum downwind concentration of NO at 5 km from the dump when the wind speed is 8 m/s at 3 m height over farmland, with a roughness length of 0.2 m. The threshold limit for NO is 25 ppm(v). Is this exceeded at 5 km from the dump ... 

For example, octane (C8H18) is the main ingredient of gasoline. When gasoline burns in a car, the products are carbon dioxide (C02), carbon monoxide (CO), water vapor (H20), and nitrous oxide (NO). 

Homocysteine decreases the bioavailability of nitrous oxide (NO) via a mechanism involving glutathione peroxidase (37). Tawakol et al. (38) reported that hyperhomocysteinemia is associated with impaired endothelium-dependent vasodilation in humans. Homocysteine impairs the NO synthase pathway both in cell culture (39) and in monkeys with hyperhomocysteinemia, by increasing the levels of asymmetric dimethylarginine (ADMA), an endogenous NO synthase inhibitor (40). Elevation of ADMA may mediate endothelial dysfunction during experimental hyperhomocysteinemia in humans (41). However, Jonasson et al. (42) did not find increased ADMA levels in patients with coronary heart disease and hyperhomocysteinemia, nor did vitamin supplementation have any effect on ADMA levels in spite of substantial plasma tHcy reduction,... 

In addition to C02, methane comes from landfills, coal mines, oil and gas operations, and agriculture. Nitrous oxide (NO) is emitted from burning fossil fuels and through the use of certain fertilizers or industrial processes. In terms of its effect on the climate, the most important greenhouse gas is C02. 

Nitrous oxide no laughing matter. Truth (Auckland, New Zealand), May 2, 2003. 

Not being aware of the earlier work, the present author first noticed the phenomenon in 1981. Geiger and Huber10 had photolyzed dimethylnitrosamine in the gas phase at 1 Torr and under 100 Torr N2 buffer. This compound fragments from the first excited singlet state into dimethylaminyl radicals and nitrous oxide NO with unity quantum yield, but neither photoproducts nor a decrease of the initial compound pressure were observed. Even after 20 h photolysis the back-reaction was complete to more than 99.9% (Scheme 6). This seemed quite puzzling because sterically unhindered aminyl radicals are transient and readily self-terminate by coupling and disproportionation. 

There are a variety of photochemical reactions involving free nitrous oxide (NO) as persistent radical. Often there is an initial fragmentation, as presented in Scheme 6 for TV, 7V-dimethyl-/V-nitro-samine. One example is the Barton reaction of nitrite esters (Scheme 15). It allows the functionalization of methyl groups in steroids and utilizes an intermediate 1,5-hydrogen atom migration, which converts the initially formed oxygen-centered radical to a carbon-centered species.69... 

Generally speaking, iron zeolites have become an active research area in the last decade from the viewpoint of environmental catalysis, covering the abatement of nitrous oxide, NO control and selective oxi tion of organics [13]. The preparation of Fe-exchanged zeolite catalysts comprises a multi-step approach ... 

Volatile organic compounds (VOQ consist of hydrocarbon emissions, most of which occur naturally. However, some VOC emissions are a result of the evaporation of hydrocarbons such as gasoline. VOCs react with sunlight, in much the same fashion as nitrous oxides (NO ), to create ground-level ozone (EPA 1995). 

Although the estimated source strengths remain uncertain, emissions from soils appear to dominate the nitrons oxide bndget (IPCC, 1990). The main biogenic sources of nitrous oxide, NO, and N2 in soils are the microbial processes of denitrification and nitrification. 

Nitrogen forms three common oxides N2O (nitrous oxide), NO (nitric oxide), and NO2 (nitrogen dioxide). It also forms two unstable oxides that we will not discuss, N2O3 (dinitrogen trioxide) and N2O5 (dinitrogen pentoxide). 

To date, no emission regulations exist for fuel cell systems. European legislation has directives for heating systems based on natural gas or Liquified Petroleum Gas (LPG). They limit nitrous oxides (NO,) to 200 ppm and carbon monoxide to 100 ppm. However, the legislation in some EU member countries are well below these values, German emission control regulations limit NO to 80 ppm and carbon monoxide to 60 ppm. 

Wuebbles, D.J. (2009) Nitrous oxide no laughing matter. Science, 326, 56-57. 

---