Nitric acid reactions, review

In the late 1960s, direct observations of substantial amounts (3ppb) of nitric acid vapor in the stratosphere were reported. Crutzen [118] reasoned that if HN03 vapor is present in the stratosphere, it could be broken down to a degree to the active oxides of nitrogen NO (NO and N02) and that these oxides could form a catalytic cycle (or the destruction of the ozone). Johnston and Whitten [119] first realized that if this were so, then supersonic aircraft flying in the stratosphere could wreak harm to the ozone balance in the stratosphere. Much of what appears in this section is drawn from an excellent review by Johnston and Whitten [119]. The most pertinent of the possible NO reactions in the atmosphere are... 

The one-electron oxidation of iV-benzylphenothiazine by nitric acid occurs in the presence of /i-cyclodextrin, which stabilizes the radical cation by incorporation into its cavity. The reaction is inhibited by adamantane, which preferentially occupies the cavity. Novel Pummerer-type rearrangements of / -sulfinylphenyl derivatives, yielding /7-quinones and protected dihydroquinones, and highly enantioselective Pummerer-type rearrangements of chiral, non-racemic sulfoxides have been reviewed. A comprehensive study has demonstrated that the redox potential for 7- and 8-substituted flavins is linearly correlated with Hammett a values. DFT calculations in [3.3.n]pro-pellanes highlight low ionization potentials that favour SET oxidative cleavage of the strained central C-C bond rather than direct C-H or C-C bond attack. Oxidations and reductions in water have been reviewed. ... 

The oxidation of primary and secondary alcohols by stable organic nitroxyl radicals has been reviewed.111 The kinetics of reactions of alkanes and arenes with peroxynitrous acid suggest the participation of the same active oxidizing species in both gas and aqueous phase HOONO or its decomposition product OONO. 112 The oxidation of the alkaloids reserpine and rescinnamine by nitric acid has been studied.113... 

Nitric oxide (NO-) is generated enzymatically from glutamate by the nitric acid synthase and is responsible for a large number of diverse biological processes (for a review, see Nathan 1992 for spin trapping of the ensuing radicals, see Tsai et al. 2000). It was soon realized that an excess production of NO- is toxic, and a part of its toxicity was attributed to its reaction with 02-, i.e the formation of peroxynitrite [reactions (30) and (31)] (Beckman et al. 1990 for a review, see Murphy et al. 1998). 

Lithium silylamides are solids with definite melting points and they may often be distilled in vacuo without decomposition. They are stable in air, but are sensitive against moisture. They decompose explosively when heated with oxygen or treated with concentrated nitric acid. Further reactions of silylamides can be found in reviews 1 2,8. 

Having reviewed photochemical valence adjustment of Np in nitric acid solution, we will briefly consider the effect of heterogeneous Pt particle catalysts on Np speciation reactions in the dark before discussing applications of heterogeneous photocatalysis in Np redox chemistry. 

Abstract Synthesis methods of various C- and /V-nitroderivativcs of five-membered azoles - pyrazoles, imidazoles, 1,2,3-triazoles, 1,2,4-triazoles, oxazoles, oxadiazoles, isoxazoles, thiazoles, thiadiazoles, isothiazoles, selenazoles and tetrazoles - are summarized and critically discussed. The special attention focuses on the nitration reaction of azoles with nitric acid or sulfuric-nitric acid mixture, one of the main synthetic routes to nitroazoles. The nitration reactions with such nitrating agents as acetylnitrate, nitric acid/trifluoroacetic anhydride, nitrogen dioxide, nitrogen tetrox-ide, nitronium tetrafluoroborate, V-nitropicolinium tetrafluoroborate are reported. General information on the theory of electrophilic nitration of aromatic compounds is included in the chapter covering synthetic methods. The kinetics and mechanisms of nitration of five-membered azoles are considered. The nitroazole preparation from different cyclic systems or from aminoazoles or based on heterocyclization is the subject of wide speculation. The particular section is devoted to the chemistry of extraordinary class of nitroazoles - polynitroazoles. Vicarious nucleophilic substitution (VNS) reaction in nitroazoles is reviewed in detail. 

N03 is generated with difficulty in aqueous solution, the primary technique being radiolysis of concentrated nitric acid or nitrate-containing solutions. Its chemistry has recently been reviewed by Neta and Huie (227). Berdnikov and Bazhin gave the first estimate of E° for the N03/N03- couple as 2.3 + 0.1 V (45). This was obtained from gas-phase data and estimated hydration energies. A recent direct measurement of the equilibrium constant for the N02 + N03 N203 reaction... 

Reagents for amination, nitrosation and nitration of tertiary alkylamines are discussed in the appropriate reviews listed in Sections 6.1.3.1.4 and 6.I.3.I.5. Tertiary amines can be nitrosated with dealkylation by dinitrogen tetroxide for example, 1-methylpiperidine gave 1-nitrosopiperidine (80%). lliis reaction probably starts by one-electron oxidation of the amine, the aminium ion then undergoing dealkylation. Other oxidative d ylations and dealkylations include the formation of iV-nitrosodibenzylamine in high yield from the acid chloride (PhCH2)2NCOCl and sodium nitrite and the conversion of the amine (43) into the nitramine (44) with nitric acid. ... 

Data have been presented on the kinetics of nitration of acetanilide in mixtures of nitric and sulfuric acids. A review discusses the several mechanisms operative in the nitration of phenol including / ara-selective nitrosation-oxidation and mechanisms involving phenoxy radical-nitrogen dioxide reaction yielding a 55 45 ortho para nitration ratio. The kinetics of mononitration of hiphenyl-2-carhoxylic acid have heen investigated in several solvents. The maximum ortho para product ratio of 8.4 is observed in tetrachloromethane. Nitration products were not formed in the presence of dioxane. Quantum-chemical AMI calculations were performed and the predominant formation of the ortho-ratio product is accoimted for hy stabilization of the (T-complex hy the carboxyl group. ... 

The reactivity of thiazole to nitration has been well reviewed <1984CFIEC(6)235>. Recently, nitration at C-4 of 2,5-dimethylthiazole 62 was accomplished with trifluoroacetic anhydride (TFAA) and fuming nitric acid at —15°C as shown in Scheme 9 to give the product 63 in 67% yield <2005ARK179>. The nitration of thiazole itself was not studied in this work due to poor solubility under the reaction conditions <2005ARK179>. See also Section 4.06.7.2. 

Nitrating medium, that is, nitric acid or mixtures of nitric acid with sulphuric acid or other agents promoting the formation of nitroxonium cation, is obviously a strongly oxidizing medium, hence a number of side reactions — mainly oxidation reactions — take place during nitration. This was described in Vol. I (pp. 75, 437) and more recently reviewed in a number of excellent papers [84-86]. 

Popova, Slavtscheva, and Gospodinov [86POP/SLA] determined the solubility of aluminium selenite in dilute nitric acid. The preparation and composition of the selenite is not discussed. It is assumed to have the formula Al2(Se03)3-6H20(cr) by the review. The solubility product calculated in the paper, see Appendix A, for Reaction (V.65),... 

The dimeric, cychc anhydrides reviewed by McDonald, and formed during the acetolysis and subsequent hydrolysis of fructans, have now been obtained in much higher yields by the use of fuming nitric acid. However, during these reactions, the fructofuranose form was already present, before ring-closure between adjacent molecules occurred to form the stable ring... 

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