Nitrite aqueous chemistry

Nitric oxide is the simplest thermally stable odd-electron molecule known and, accordingly, its electronic structure and reaction chemistry have been very extensively studied. The compound is an intermediate in the production of nitric acid and is prepared industrially by the catalytic oxidation of ammonia (p. 466). On the laboratory scale it can be synthesized from aqueous solution by the mild reduction of acidified nitrites with iodide or ferrocyanide or by the disproportionation of nitrous acid in the presence of dilute sulfuric acid ... 

The monovalent Co chemistry of amines is sparse. No structurally characterized example of low-valent Co complexed exclusively to amines is known. At low potentials and in non-aqueous solutions, Co1 amines have been identified electrochemically, but usually in the presence of co-ligands that stabilize the reduced complex. At low potential, the putative monovalent [Co(cyclam)]+ (cyclam = 1,4,8,11-tetraazacyclotetradecane) in NaOH solution catalyzes the reduction of both nitrate and nitrite to give mixtures of hydroxylamine and ammonia.100 Mixed N-donor systems bearing 7r-acceptor imine ligands in addition to amines are well known, but these examples are discussed separately in Section 6.1.2.1.3. 

Diketo oxime 43 (Scheme 27) find extensive use in organic synthesis. These compounds are useful building blocks in five-membered heterocyclic chemistry. These oximes can be used for the synthesis of pyrroles , thiazoles , oxazoles and pyrazoles . The diketo oxime 43 was synthesized in high yield by addition of an aqueous solution of sodium nitrite to a 0°C solution of 1-benzoylacetone 42 in AcOH . ... 

It is known from studies carried out over many decades that oxides of nitrogen at high concentrations dissolve in aqueous solution and react to form species such as nitrate and nitrite. With the focus on acid deposition and the chemistry leading to the formation of nitric and sulfuric acids during the 1970s and 1980s, a great deal of research was carried out on these reactions at much lower concentrations relevant to atmospheric conditions (for reviews, see Schwartz and White, 1981, 1983 and Schwartz, 1984). 

As expected based on our knowledge of gas-phase chemistry, in addition to the Fenton type chemistry involving iron, photolysis of Os, H202, HONO, and HNO-, are all potential OH sources in clouds and fogs. In addition, the photolysis of nitrite, nitrate, and HOJ in aqueous solutions can also form OH. In short, there are many potential sources of OH in clouds and fogs. 

The chemistry of nitrite at acidic pH is closely related to that of nitrosonium ion described earlier. The pfC, of nitrous acid is around 3.4-3.6, though precise measurement is difficult because of its rapid secondary reactions. Acidification of nitrite produces nitrous acid, which is in reversible equilibrium with nitrosonium ion and hydroxide ion (Turney and Wright, 1959), although in aqueous solu-... 

Bonner, F. T., and Pearsall, K. A. (1982). Aqueous nitrosyliron(ll) chemistry. 1. Reduction of nitrite and nitric oxide by iron(ll) and (trioxodinitrato)iron(ll) in acetate buffer. Intermediacy of nitrosyl hydride. Inorg. Chem. 21, 1973-1978. 

Diazodinitrophenol (DDNP, Dinol) 4,6-Dinitrobenzene-2-diazo-l-oxide, or diazodinitrophenol as it is more commonly called, occupies a place of some importance in the history of chemistry, for its discovery by Griess56 led him to undertake his classic researches on the diazonium compounds and the diazo reaction. He prepared it by passing nitrous gas into an alcoholic solution of picramic acid, but it is more conveniently prepared by carrying out the diazotization in aqueous solution with sodium nitrite and hydrochloric acid. 

It is likely that as further anhydrous nitrates are prepared, further examples of such behavior will be found. Certain ruthenium nitrates also give nitrite on hydrolysis (28). All metal nitrates which by their covalent bonding can release NO2 radicals during reaction need not necessarily give nitrite on hydrolysis the latter is a complicated process which involves the coordination chemistry of the metal. For example, copper nitrate gives only nitrate ions in aqueous solution, but its reactions with ethers are at present interpreted on a free-radical basis. 

The aqueous solution chemistry of nitrous acid and nitrites has been extensively studied. Some reduction potentials involving these species are given in Table 11.4 (p. 434) and these form a useful summary of their redox reactions. Nitrites are quantitatively oxidized to nitrate by permanganate and this reaction is used in titrimetric analysis. Nitrites (and HNOa) are readily reduced to NO and NaO with SO2, to H2N2O2 with Sn(II), and to NH3 with HaS. Hydrazinium salts yield azides (p. 432) which can then react with further HNOa ... 

APPENDIX 7.3 AQUEOUS-PHASE NITRITE AND NITRATE CHEMISTRY 7.A.4 NO Oxidation... 

CHEMISTRY OF THE ATMOSPHERIC AQUEOUS PHASE TABLE 6.A.5 Nitrite and Nitrate Chemistry... 

Nitrite Solutions—The Sulfa-Check and Hondo HS-lOO Processes. The Sulfa-Check process, developed by NL Treating Chemicals/NL Industries, Inc. and marketed by Exxon Chemical Co., is based on the use of a buffered aqueous solution of sodium nitrite to absorb and destroy hydrogen sulfide. The Hondo HS-lOO process, offered by Hondo Chemicals, is believed to involve similar chemistry using potassium instead of sodium nitrite. The Sulfa-Check process is reviewed in the following section as an example of a nitrite-based system because considerable data are available on the technology (Dobbs, 1986 Bhatia and Allford, 1986 Bhatia and Brown, 1986 Schaack and Chan, 1989). 

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