Nitroxylic acid

Nitroxylic acid, HiNO . Yellow NajNOa formed by electrolysis NaN02 in NHj. Structure unknown free acid unknown. Nitramide, H2NNO2. A weak acid. 

H2NO2 nitroxylic acid H2SO2 sulfoxylic acid... 

The name nilroxyl should not be used for this group because of the use ofibe trivial name nitroxylic acid for H2NOj... 

J. Biehringer and W. Borsum suggested that nitrosylsulphuric acid exists in two tautomeric forms, H0.S02.0. N0 + H0. S02.N02, which are in equilibrium in cone, sulphuric acid soln. and in the molten state. In support of this, they found that in some cases it can react simultaneously as two different acids, for, when a soln. of dimethylaniline in cone, sulphuric acid is slowly treated with the requisite amount of sodium nitrite, both p-nitrodimethylaniline and p-nitroso-dimethylaniline are produced, the former represents the nitrosyl-acid and the latter the nitroxyl-acid. At 10° to 15°, the yields are respectively 8-33 and 7+5... 

In this system the nitroxyl and acid act as catalysts and H2O2 is consumed. A similar cyclic mechanism of chain termination takes place when the system alcohol + nitroxyl + acid or the system hydrogen peroxide + quinonimine + acid are introduced into oxidized hydrocarbon. 

H4N2O4 Nitroxylic (hydronitrous) acid Explosive sodium salt known Na4[02NN02] ... 

The reaction is based on an early observation by Angeli and Ahrens that Piloty s acid converted aldehydes to hydroxamic acids, and this has formed the basis of the Angeli-Rimini aldehyde test. Di Maio and Tardella propose the above reaction sequence, consistent with the observed second-order kinetics. The possibility that benzenesulfon-hydroxamic acid would decompose in alkali to give nitroxyl (HNO)... 

Nitryl Perchlorate (Nitroxyl Perchlorate). N02C104, mw 145.47, white cryst mp, decomps rapidly at 120° deflagrates on rapid heating Can be prepd by the action of cone nitric acid on perchloric acid ... 

Organic acids retard the formation of nitroxyl radicals via the reaction of the peroxyl radical with the aminyl radical [10], Apparently, the formation of a hydrogen bond of the >N H0C(0)R type leads to the shielding of nitrogen, which precludes the addition of dioxygen to it, yielding the nitroxyl radical. Thus, the products of the oxidation of alcohols, namely, acids have an influence on the mechanism of the cyclic chain termination. 

A new interesting branch of the modern antioxidant chemistry deals with the cyclic mechanisms involving acid catalysis. The first inhibiting system of this type was discovered in 1988 [44]. It consisted of an alcohol (primary or secondary), a stable nitroxyl radical TEMPO, and... 

The resulting products, such as sulfenic acid or sulfur dioxide, are reactive and induce an acid-catalyzed breakdown of hydroperoxides. The important role of intermediate molecular sulfur has been reported [68-72]. Zinc (or other metal) forms a precipitate composed of ZnO and ZnS04. The decomposition of ROOH by dialkyl thiophosphates is an autocata-lytic process. The interaction of ROOH with zinc dialkyl thiophosphate gives rise to free radicals, due to which this reaction accelerates oxidation of hydrocarbons, excites CL during oxidation of ethylbenzene, and intensifies the consumption of acceptors, e.g., stable nitroxyl radicals [68], The induction period is often absent because of the rapid formation of intermediates, and the kinetics of decomposition is described by a simple bimolecular kinetic equation... 

In contrast to nitric oxide, which is firmly identified in biological systems and for which numerous (but not all) functions are known, the participation of other nitrogen species in biological processes is still hypothetical. At present, the most interest is drawn to the very reactive nitroxyl anion NOT It has been shown that nitroxyl (or its conjugate acid, HNO)... 

However, the in vivo sources of nitroxyl production remain uncertain. Some authors suggested that nitroxyl anion might be generated by NO synthases [81,82] or during the decomposition of nitrosothiols [83]. It has also been proposed [81] that the primary product of NO synthase is not nitric acid but nitroxyl anion, which is next oxidized by SOD to NO ... 

In contrast, the reaction of acid-catalyzed nucleophilic addition of alcohols to derivatives of AH -imidazol-1 -oxide (219) and (224) leads only to nitronyl nitroxyl (221) and imino nitroxyl (274) radicals (518). 

N-Hydroxy-N-nitrosamines with an aliphatic group at O2 produce a compound stable to aqueous acid and base (Fig. 3.4, 29) [158], whereas all other N-hydroxy-N-nitrosamines are susceptible to hydrolysis and appropriate 02-derivatives also render these materials vulnerable. The hydrolysis endpoint is the formation of nitroxyl (HNO) [which dimerizes to form nitrous oxide (N20)] and a C-nitroso compound. These products are formed from aryl [159] and alkyl bound unsubstituted diazenium-diolates as well as Oralkylated derivatives [160]. Studies of the solvolysis of Oi-alkyl derivatives are complicated by their tendency to decompose via competing radical pathways [161], but the Oi-benzyl derivatives are unique in that they hydrolyze back to the original synthetic precursors (Scheme 3.14) [162]. 

N, O-Diacylated or O-alkylated N-hydroxysulfonamides release nitroxyl (HNO) upon hydrolysis or metabolic dealkylation, as determined by gas chromatographic identification of nitrous oxide in the reaction headspace [27-29, 38]. Scheme 7.5 depicts the decomposition of a representative compound (7) to a C-acyl nitroso species that hydrolyzes to yield HNO. Either hydrolysis or metabolism removes the O-acyl or O-alkyl group to give an N-hydroxy species that rapidly decomposes to give a sulfinic acid and an acyl nitroso species. This C-acyl nitroso species (8) hydrolyzes to the carboxylic acid and HNO (Scheme 7.5). These compounds demonstrate the ability to relax smooth muscle preparations in vitro and also inhibit aldehyde dehydrogenase, similar to other HNO donors [27, 29]. 

The method uses a simple electrode made of a thin film of sol-gel organosilica doped with nitroxyl radicals deposited on the surface of an indium tin oxide (ITO) electrode. Thus, whereas in water benzyl alcohol is rapidly oxidized to benzoic acid, the use of the hydrophobic sol-gel molecular electrode TEMPO DE affords benzaldehyde only (Figure 1.9), with an unprecedented purity, which is highly desirable for the fragrance and pharmaceutical industries where this aromatic aldehyde is employed in large amounts. 

Oxidation of —CHtOH — —CHO (cf., 12,479-480). This oxidation can be effected in high yield with sodium hypochlorite (slight excess) in buffered H20/ CH2C12 with this nitroxyl radical and KBr as the catalysts.1 The oxidation is exothermic, and the temperature should be maintained at 0-15° with a salt-ice bath. Saturated primary alcohols are converted to aldehydes in 88-93% yield yields are lower in the case of unsaturated substrates. Addition of quaternary onium salts permits further oxidation to carboxylic acids. 

The most important reaction of benzenesulphohydroxamic acid is its decomposition by alkalis. This decomposition does not consist in a reversal of the process of formation (i.e. conversion into benzenesul-phonic acid and hydroxylamine). An exchange of the state of oxidation takes place benzenesulphinic acid and nitroxyl are produced ... 

It was mentioned on p. 193 that benzene sulphohydroxamic acid is decomposed by alkali into benzene sulphinic acid and the very unstable compound nitroxyl, 0=NH. If nitroxyl is produced in the presence... 

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