Nitric oxide

Nitric oxide was approved by the FDA in 1999 for use as a vasodilator in the treatment of hypoxic respiratory failure in full- and near-term infants. It is a colorless and essentially odorless gas with a very narrow therapeutic window for patients. Acute exposure effects include mucous membrane 

Nitric oxide (NO) is produced by many cell types, including endothelial cells, and has functions ranging from neurotransmission to vasodilatation. NO may be useful to treat bronchodilatation in clinical conditions and is used successfully in patients with persistent fetal circulation and pulmonary hypertension. NO is also a toxic oxidant. 

Nitric Oxide.—Nitric oxide is the most stable of the odd molecules. For the first of the two structures I and II 

The properties of the molecule are accounted for by this structure. The extra energy of the three-electron bond stabilises the molecule relative to structure I to such extent that the heat of the reaction 2NO — NaO is small,8 and the substance does not polymerize in the gas phase. 

This structure, which may be described as involving a 2 bond, is expected to lead to a bond length intermediate between that for a double bond and that for a triple bond. The N—O single-bond length is 1.44 A (Sec. 7-2), and the double-bond and triple-bond lengths may be taken as 0.04 A less than for N—N and N=N, and hence equal to 1.20 A and 1.06 A, respectively. This triple-bond value agrees well with the experimental value 1.062 A for NO+, which has the structure 

A study of the hyperfine structure of the electron spin magnetic resonance spectrum, resulting from the interaction with the nuclear spins, has led to the conclusion9 that structure I contributes 65 percent and structure II35 percent, and that the odd electron occupies a 2pr orbital with 2.5 percent s character. 

The electric dipole moment of the molecule is small, about 0.16 D. Structure I would lead to a moment with the oxygen atom negative, because of the partial ionic character of the bonds this moment is neutralized by structure II. 

Nitric oxide (NO), nitrous oxide (N2O), dinitrogen (N2), and ammonia (NH3) are constituents of the Earth s atmosphere. They play important roles in the chemistry and climate of the present-day Earth. Moreover, they are intermediates of the oceanic nitrogen cycle. In contrast to most of the other components of the oceanic nitrogen cycle, they exist as dissolved gaseous molecules. Being gases they can be transferred across the seasurface-troposphere interface. 

In this chapter, I intent to give an overview about the current knowledge on the oceanic distribution and pathways of NO, N2O, N2, and NH3 which has increased considerably since the publication of Gaseous nitrogen compounds in the sea by Scranton (1983). 

Fundamental physical processes such as gas diffusivities in seawater and air-sea gas exchange as well as details of measurement techniques for dissolved gases in seawater are not discussed in the context of this chapter. 

Because of the heavily increasing number of publications (especially for N2O) it is not possible to give a comprehensive overview on aU aspects of the gases discussed in this chapter. Therefore, it was necessary to focus the review on one particular topic—the water-column distribution. However, to cover emerging new developments, sedimentary and atmospheric measurements/processes are introduced when necessary. I tried to document the most actual developments, however, especially for N2O, it was not possible to consider aU relevant publications. 

To have a high degree of transparency, I predominately used pubhcations in international journals or books. Grey Hterature such as PhD thesis or submitted articles etc. is cited only when unavoidable. 

Nitric oxide (NYE-trik OK-side) is a sweet-smelling, colorless gas that can be liquefied to make a bluish liquid and frozen to produce a bluish-white snow-like solid. It is one of five oxides of nitrogen, the others being nitrous oxide (N20), nitric oxide (NO), dinitrogen trioxide N203), and nitrogen dioxide (N02). Nitric oxide was first discovered in 1620 by Flemish physician and alchemist Jan Baptista van Helmont (1580-1635 or 1644). 

Nitric oxide is used in the production of nitric acid, ammonia, and other nitrogen-containing compounds. It is also formed as a byproduct of the combustion of coal and petroleum products. As such, it is a major contributor to air pollution. 

Nitrogen and oxygen are the two most abundant gases in the atmosphere. Since both elements are relatively inactive, 

Nitrogen monoxide. Red atom is oxygen and blue atom is nitrogen. PUBLISHERS RESOURCE CROUP 

The most important industrial use of nitric oxide is in the preparation of other nitrogen-containing compounds, especially nitrogen dioxide (N02), nitric acid (HN03), and nitrosyl chloride (N0C1). It also finds some application in the bleaching of rayon (a synthetic, or artificially created, fabric) and as a polymerization inhibitor with certain compounds such as propylene and methyl ether. Such compounds have a tendency to react with each other to form large, complex molecules known as polymers. 

Nitric Oxide. Nitrogen(ii) oxide reacts with the complex [Co(NO)(Ph3P)3] in benzene or toluene solution to give [Co(NO)2(ONO)(Ph3P)], PhjPO, N2, and N2O. The same reaction, carried out with a molar ratio 1 2 (Co complex NO), gives the trinuclear complex [Co3(NO)7(Ph3P)3], which is capable of catalysing the disproportionation of NO. The catalysed. eduction of NO, from effluent gas 

Nitrogeniiii) Species. The reaction of the nitrosonium salt NO BF7 with the dioxygen complex [Pt(PPh3)202] in acetonitrile solution produces 

Stein and F. A. Hohorst, J. Inorg. Nuclear Chem. - Herbert H. Hyman Memorial Volume., 1976, 

NO2-N2O4. Both of the reaction studies on O2 SbFs already mentioned in connection with NO also included the reaction with NO2, which proceeds according to reaction (4). In addition, the Russian group have reported that the 

2XeF+SbFg + ZNOj 2NOJ SbFg + Xe + XeFj (5) 

Nitric oxide at room temperature is a colorless, nonflammable, toxic gas. Nitric oxide in the presence of air forms brown fumes of nitrogen dioxide, which is extremely reactive and a strong oxidizing agent. The conversion of nitric oxide to nitrogen dioxide is rate dependent on the concentration of oxygen and the square of the concentration of nitric oxide. It also reacts vigorously with fluorine oxides and, when moisture is present, chlorine. Nitric oxide is shipped in a nonliquefied form at a cylinder pressure of 514.7 psia (3549 kPa abs) at 70°F (21.1°C). 

Nitric oxide is an oxidizer and will support combustion. It will react with oxygen, oxidizing agents, halides, and hydrocarbons. Nitric oxide is noncorrosive and most structural materials are unaffected however, in the presence of moisture, corrosion can develop with the formation of nitrous and nitric acids. 

Nitric oxide is unstable at higher pressures and temperatures and has been known to cause violent rupture of a container with an adequate energy input. 

Nitric oxide is available in a minimum purity of 98.5 percent or 99.0 percent. 

Nitric oxide is an important intermediate in the production of nitric acid. Fluorine, chlorine, and bromine react with nitric oxide to form the corresponding nitrosyl halide. It is also used in making mixtures for calibration standards for stationary and mobile exhaust emission measurements. 

Nitric oxide was approved by the FDA in 1999 for use as a vasodilator in the treatment of hypoxic respiratory failure in full- and near-term infants. It is a colorless and essentially odorless gas with a very narrow therapeutic window for patients. Acute exposure effects include mucous membrane irritation and drowsiness. More serious effects include delayed pulmonary toxicity and damage to the central nervous system effects. Exposed employees may seem relatively asymptomatic at the time of exposure. It can take as long as 72 hours to manifest clinical symptoms. OSHA classifies nitric oxide as a highly hazardous substance. 

The gaseous free radical nitric oxide (NO), a non-conventional neural messenger, is synthesized in neurons by the enzyme nitric oxide synthase (NOS), which can be revealed in histological sections by NADPH-diaphorase histochemistry or NOS immunohisto-chemistry. The role of NO in neural signaling has raised considerable interest (see, for example, Schmidt and Walter, 1994), stemming also from the finding that NOS has a discrete distribution in subsets of brain neurons, including intense expression in neuronal subsets of the striatum (Vincent, 2000). 

CONSTITUTIVE EXPRESSION IN MIDBRAIN DOPAMINERGIC NEURONS OF MOLECULES IMPLICATED IN NEURAL-IMMUNE INTERACTIONS 

One of the relatively few simple odd electron species, nitric oxide is an intriguing heteronuclear diatomic and the parent member of the oxides of nitrogen. Like carbon monoxide, nitric oxide has a long and distinguished coordination chemistry, but unlike CO, it forms very few binary metal 

As with carbonyl coordination, the degree of backbonding in the linear mode of coordination is influenced by the complex charge, metal oxidation state and nature of the ancillary ligands. An example of how both the oxidation state and the relative d orbital energies influence vN0 is shown dramatically in the pentacyanonitrosyl systems M(NO)(CN) (z = 2, M = Fe, 

The bent mode of nitrosyl coordination, as represented by Lewis structure (38), provides the nitrosyl with structural uniqueness. 

The structural studies of nitrosyls have shown to date that the bent nitrosyl ligand invariably occurs at the apical position of a square based pyramid or a distorted octahedron in which the metal ion configuration assuming NO- coordination is d6. Despite numerous electronic structural descriptions (168, 169,198-200), it is not totally clear why fully bent nitrosyls with M—N—O bond angles of 120° have not been found in other geometries such as the square plane and the trigonal bipyramid. 

The NO+ and NO- modes of coordination differ by two electrons in terms of formal charge. Interconversion of these two bonding modes becomes feasible when the bound metal ion possesses two complementary oxidation states. It has been proposed that this interconversion, which corresponds to an intramolecular redox reaction, represents a unique and facile way to achieve coordinative unsaturation at the metal center with the nitrosyl acting as an electron pair reservoir (201). Interconversion of linear and bent nitrosyls has been reported in the unusual complex Ru(NO)2C1-(PPh3)2+ that possesses one linear and one bent nitrosyl, structure (39) (202). 

It is only relatively recently that the biological importance of nitric oxide ( NO) has been appreciated (Palmer et al., 1987 Moncada et al., 1988). This radical has a structure similar to that for 02 , except that it has 2 e less, i.e., it is isoelectronic with 02+, just as NO- is a triplet-state species iso-electronic with 02. It has only a minor tendency to dimerise, and it is not clear to what extent its reactivity in biological reactions is linked to its radical character. It is very readily oxidised to N02 whose possible importance in biological reactions seems to be unknown. These two paramagnetic oxides are closely related to N02 and N03 ions. For example, N02 disproportionates to give nitrite and nitrate in acidic solution, but N02 in acid gives N03- + NO [1.11]. 

Thus nitrite ions are a direct source of NO in acidic media. The other important reaction is that with oxygen [1.12], which is quite rapid and effectively irreversible. This means that NO will only reach high concentrations in the absence of oxygen. 

C(NH2)2+ unit of arginine, via the formation of hydroxylamine. It can be characterized by ESR spectroscopy using deoxy-myoglobin or -haemoglobin with which it reacts to give nitrosyl derivatives having well-defined spectra. Its chief biological role seems to be as a vasorelaxant (Moncada et al., 1988). 

Small alkyl radicals such as methyl CCH3) do not seem to play an important role in biology. (Except that it might be significant that methyl radicals are readily detected by ESR spectroscopy in various flints (cherts) (Griffiths et al., 1982). One wonders whether, in a methane-rich atmosphere, methyl radicals might be of some biological importance.) 

However, allyl-type radicals are thought to be important in the au-toxidation of membrane lipids etc. (Chapter 5). These are more stable because the unpaired electron is delocalized on the two outer carbon atoms. 

Exposure to pathobiological stressors causes the formation or release of mediators other than cytokines and ROS. These include stress-induced hormones and nitric oxide (NO). Stress responses stimulate the hypothalamic-pituitary axis causing the release of adrenocorticotropin, thereby elevating glucocorticoid levels. Glucocorti- 

In contact with the eyes, the liquid produces severe burns, which may result in permanent damage and visual impairment. On the skin, the liquid or concentrated vapor produces immediate, severe, and penetrating burns concentrated solutions cause deep ulcers and stain the skin a bright yellow or yellowish-brown color.Dilute solutions of nitric acid produce mild irritation of the skin and tend to harden the epithelium without destroying it. 

Nitric acid was not mutagenic in limited studies. There is no information regarding the carcinogenic properties of nitric acid, but an association between incidences of laryngeal cancer and exposure to acid mists has been indicated.  

The 2003 ACGIH threshold limit value-time-weighted average (TLV-TWA) is 2 ppm (5.2mg/m ) with a short-term excursion limit (STEL)/ceiling of 4ppm (lOmg/m ). 

National Institute for Occupational Safety and Health Criteria for a Recommended Standard. .. Occupational Exposure to Nitric Acid. DHEW (NIOSH) Pub No 76-141, pp 35-36. Washington, DC, US Government Printing Office, 1976 

Hygienic Guide Series Nitric acid. Am Ind Hyg Assoc J 2SA26-A2, 1964 

The ability of NO to react at least 1000-times more rapidly with free Hb than with Hb in red blood cells may have important implications for sickle-cell patients, who have increased levels of free Hb in their blood. The EPR examination of blood taken from such patients following the inhalation of NO has revealed elevated levels of Hb-Fe(III) compared with controls. Elevated free haem levels in the patients were associated with decreased NO bioavailability during the infusion of the NO donor nitroprusside, resulting in decreased blood flow.71 

Stoyanovsky and colleagues have demonstrated OH production from HNO, which they proposed involves its dimerisation to d.s-hyponitrous acid (HO- 

N = N-OH), followed by homolytic fission to N2 and OH. Production of the radical was more efficient at pH 6.0 than 7.4 (where, through isomerisation, decomposition to N20 and H20 increasingly occurs), suggesting that HNO may be a toxin in tissues subjected to acidosis.89 

The energy for these reactions comes from the oxidation of nicotine-adenine dinucleotide phosphate (NADPH) to NADP and from the conversion of molecular oxygen to water. 

Synthesis of this enzyme is triggered by external stimuli, such as cytokines, released by cancer cells. Once synthesized, the enzyme produces large quantities of NO, which then diffuses into the tumor cells, disrupting DNA synthesis and inhibiting cell growth. The other NO synthases are present at all times, but are activated in a sequence of steps dependent on Ca concentration. An activated neuron releases a chemical messenger that opens calcium channels in the next neuron. As Ca enters the nerve cell, it binds with calmodulin and the NO synthase to activate it. The reactions described earlier for formation of NO take place, and the NO then activates another enzyme, guanylyl cyclase. From this point on, the effects are uncertain, but may include diffusion back to the first cell and reinforcement of the stimulus. One of the end results seems to be relaxation of smooth muscle, related to the effect seen in blood vessels. 

In a different organism, the effect of pH on NO bound to a heme group in the protein nitrophorin 1 helps the bloodsucking insect Rhodnius prolixus obtain a meal.  

In the saliva of the insect, the pH is about 5 and the complex is stable. When the complex is injected with the saliva into the blood of a victim, the pH rises to about 7 and the NO is released. The vasodilator and anticoagulant action of the NO make it easier for the insect to draw blood from the victim. 

The chemistry of transition metal nitrosyls has been reviewed, with spectra of many types used to study the electronic structure. Bonding, as described in Chapter 13, can be thought of as a linear complex of NO, isoelectronic with CO and with NO stretching frequencies of 1700 to 2000 cm or a bent complex of NO , isoelectronic with O2 and with NO stretching frequencies of 1500 to 1700 cm . The number of electrons on the metal ion and the influence of the other ligands on the metal provide for changes from one to the other during reactions. 

To calculate values of the molar heat capacity of XO at the temperatures 45 °K, 90 °K, 120 °K, 180 K, and to compare these with experiment. 

The normal electronic state of NO is and the first excited state is ITa. The energy separation s between these states has a value given by e/k = 1.8 X 10 deg. Both states have a statistical weight 2. 

The heat capacity of NO was measured over the temperature range 127 K to 178 °K by Eucken and d Or (Nachr. Ges. Wiss. Gottingen, 1932, 107). Some representative values, corrected to zero pressure, are given in table 1. 

The equilibrium value of the molecular electronic energy at the temperature T is 

To obtain C, we have to add the classical value 52 for a rigid linear molecule. 

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Engleman R Jr, Rouse P E, Peek H M and Biamonte V D 1970 Beta and gamma band systems of nitric oxide Los Aiamos Scientific Laboratory Report no LA-4364... 

The journal Science selected nitric oxide as its Molecule of the Year for 1992... 

Our experience conditions us to focus on the organic components of the reaction—l arginine and l citrul line—and to give less attention to the inorganic one—nitric oxide (nitrogen monoxide NO) To do so however would lead us to overlook one of the most important discoveries in biology in the last quarter of the twentieth century... 

Nantokite, see Copper(I) chloride Natron, see Sodium carbonate Naumannite, see Silver selenide Neutral verdigris, see Copper(H) acetate Nitre (niter), see Potassium nitrate Nitric oxide, see Nitrogen(II) oxide Nitrobarite, see Barium nitrate Nitromagnesite, see Magnesium nitrate 6-water Nitroprusside, see Sodium pentacyanonitrosylfer-rate(II) 2-water... 

Temp. Hydrogen sulfide Methane Nitric oxide Nitrogen Oxygen Sulfur dioxide ... 

Nitric oxide Aluminum, BaO, boron, carbon disulflde, chromium, many chlorinated hydrocarbons, fluorine, hydrocarbons, ozone, phosphine, phosphorus, hydrazine, acetic anhydride, ammonia, chloroform, Fe, K, Mg, Mn, Na, sulfur... 

Ozone ALkenes, aromatic compounds, bromine, diethyl ether, ethylene, HBr, HI, nitric oxide, nitrogen dioxide, rubber, stibine... 

Pentacarbonyliron Acetic acid, nitric oxide, transition metal halides, water, zinc... 

Some heteronuclear diatomic molecules, such as nitric oxide (NO), carbon monoxide (CO) and the short-lived CN molecule, contain atoms which are sufficiently similar that the MOs resemble quite closely those of homonuclear diatomics. In nitric oxide the 15 electrons can be fed into MOs, in the order relevant to O2 and F2, to give the ground configuration... 

Figure 8.20 Nitrogen Is and oxygen Is X-ray photoelectron spectra of nitric oxide (NO) adsorbed on an iron surface. 1, Fe surface at 85 K 2, exposed at 85 K to NO at 2.65 x 10 Pa for 80 s 3, as for 2 but exposed for 200 s 4, as for 2 but exposed for 480 s 5, after warming to 280 K. (Reproduced, with permission, from Kishi, K. and Roberts, M. W., Proc. R. Soc. Land., A352, 289, 1976)...

Nitric oxides Nitric oxide synthase Nitric oxide synthases Nitrided steels Nitride fibers Nitrides... 

Other routes to acrylonitrile, none of which achieved large-scale commercial appHcation, are acetaldehyde and HCN (56), propionittile dehydrogenation (57,58), and propylene and nitric oxide (59,60) ... 

Air pollution can be considered to have three components sources, transport and transformations in the atmosphere, and receptors. The source emits airborne substances that, when released, are transported through the atmosphere. Some of the substances interact with sunlight or chemical species in the atmosphere and are transformed. Pollutants that are emitted directiy to the atmosphere are called primary pollutants pollutants that are formed in the atmosphere as a result of transformations are called secondary pollutants. The reactants that undergo transformation are referred to as precursors. An example of a secondary pollutant is O, and its precursors are NMHC and nitrogen oxides, NO, a combination of nitric oxide [10102-43-9] NO, and NO2. The receptor is the person, animal, plant, material, or ecosystem affected by the emissions. 

Pure nitroglycerin is a stable Hquid at temperate conditions. It decomposes above 60°C to form nitric oxides which in turn catalyze further decomposition. Moisture increases the rate of decomposition under these conditions. Double- and multibase propellants containing nitroglycerin have substantially shorter stabiHty Hves at 65 and 80°C than do single-base propellants. The decomposition of nitroglycerin proceeds as... 

Cellulose nitrate also has widespread use as an adhesive and coating material. Whereas stabilizers are added to products, eg, sodium carbonate as a neutralizer, many conservators are hesitant to use cellulose nitrate materials because of the inherent instabiUty and the dangers to the object from nitric acid, formed when the nitric oxide combines with moisture. 

Nitric oxide and OF2 inflame on contact emission and absorption spectra of the flame have been studied (24). Oxygen difluoride oxidizes SO2 to SO, but under the influence of uv kradiation it forms sulfuryl fluoride [2699-79-8] SO2F2, and pyrosulfuryl fluoride [37240-33-8] S20 F2 (25). Photolysis of SO —OF2 mixtures yields the peroxy compound FSO2OOF [13997-94-9] (25,26). 

Nitrosyl chloride (178), nitrosyl chloride—hydrogen fluoride (NOF -3HF, NOF -6HF) (179), nitrous acid—hydrogen fluoride solutions (180,181), or nitrogen trioxide (prepared in situ from nitric oxide and oxygen) (27) can be used in place of sodium nitrite in the dia2oti2ation step. 

Reduction of metal oxides with hydrogen is of interest in the metals refining industry (94,95) (see Metallurgy). Hydrogen is also used to reduce sulfites to sulfides in one step in the removal of SO2 pollutants (see Airpollution) (96). Hydrogen reacts directiy with SO2 under catalytic conditions to produce elemental sulfur and H2S (97—98). Under certain conditions, hydrogen reacts with nitric oxide, an atmospheric poUutant and contributor to photochemical smog, to produce N2 ... 

Fig. 5. NO formation in a hydrogen engine having spark at 17° before top-dead center (BTC) rpm, 2900 and compression ratio, 5.5 1, where A is nitric oxide B, backfire C, power and D, brake thermal efficiency, (a) Effect of equivalence ratio, ( ) and (b), effect of water induction at 0 = 0.625.

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