Nitrous acid formation

Akimoto, H H. Takagi, and F. Sakamaki, Photoenhancement of the Nitrous Acid Formation in the Surface Reaction of Nitrogen Dioxide and Water Vapor Extra Radical Source in Smog Chamber Experiments, lnt. J. Chem. Kinet., 19, 539-551 (1987). 

We assume that the contribution to G(HN02) from those free radicals H and OH which escape from the spur in the absence of isopropyl alcohol is about 0.5 [GH — G0h + 0.7] = 0.5 [3.7 — 2.6 + 0.7] = 0.9. Figure 9 and Table I show that G(HN02) is increased from this value of 0.9 to 2.2 by the presence of 5.0M sodium nitrate. Two effects of 5.0M sodium nitrate are an increase in GH2o2 °f — 0.4 with concomitant increase in G(HN02) of /— 1.3. These effects of nitrate ion cannot be interpreted quantitatively by the proposal of Bednar (4) that nitrous acid formation is accompanied by hydrogen peroxide formation by reaction of nitrate ion with excited water ... 

Consideration of material balance leads us to conclude that nitrous acid formation is accompanied by both hydrogen peroxide and oxygen formation. 

Calvert, J. G., Yarwood, G., and Dunker, A. (1994) An evaluation of the mechanism of nitrous acid formation in the urban atmosphere, Res. Chem. Intermediates 20, 463-502. 

No explanation for the mechanism of introduction of the hydroxyl group Weis given eUid no attention wcis given to nitrous acid formation. 

To determine whether nitrous acid is formed only from the toluene present, the experiment wais repeated with MNT instead of toluene as the aromatic compound present initially. Nitrous acid was produced at approximately the same rate as from toluene (Fig.3). This indicates that the decrecise in rate of nitrous acid formation towards the end of the meiin reaction is because the nitric acid has been nearly used up, rather than being due to the replacement of toluene by MNT. 

The function i zo(relationship accounting for the self-catalyzed nature of the nitrous acid formation process ... 

Consider the propagation process analyzed in Reference (9) in which the capacitance term in Eq. (9) may be neglected. As noted above, the current due to nitrous acid formation rises slowly, and it is this parameter which is actually responsible for the wire returning to the original passivated state. On the other hand, it is clear that the impulse propagation velocity is controlled by the processes in the activation zone where (p > (p. Therefore, in this zone the current due to nitrous acid formation may be ignored, and then, substituting... 

Akimoto, H., K. Takagi and F. Sakamaki (1987) Photoenhancement of the nitrous acid formation in the surface reaction of nitrogen dioxide and water vapor Extra radical source in smog chamber experiments. International Journal of Chemical Kinetics 19, 539-551. 

Ab initio molecular orbital calculations on N0+-(H20) cluster ions. Part I Minimum-energy structures and possible routes to nitrous acid formation ... 

Formation of nitrosaminey RgN NO. (a) From monomethylaniline. Dissolve I ml. of monomethylaniline in about 3 ml. of dil. HCl and add sodium nitrite solution gradually with shaking until the yellow oil separates out at the bottom of the solution. Transfer completely to a smdl separating-funnel, add about 20 ml. of ether and sh e. Run off the lower layer and wash the ethereal extract first with water, then with dil. NaOH solution, and finally with w ter to free it completely from nitrous acid. Evaporate the ether in a basin over a previously warmed water-bath, in a fume cupboard with no flames near. Apply Liebermann s reaction to the residual oil (p. 340). 

Tertiary aliphatic - aromatic amines, unlike those of the aliphatic series, react with nitrous acid with the formation of G-nitroso compounds the nitroso group enters almost exclusively in the para position if available, otherwise in the ortho position. Thus dimethylaniline yields />-nitrosodiniethylaniline ... 

Primary aromatic amines differ from primary aliphatic amines in their reaction with nitrous acid. Whereas the latter yield the corresponding alcohols (RNHj — ROH) without formation of intermediate products see Section 111,123, test (i), primary aromatic amines 3neld diazonium salts. Thus aniline gives phcnyldiazonium chloride (sometimes termed benzene-diazonium chloride) CjHbNj- +C1 the exact mode of formation is not known, but a possible route is through the phenjdnitrosoammonium ion tlius ... 

In experiments on the nitration of benzene in acetic acid, to which urea was added to remove nitrous acid (which anticatalyses nitration 4.3.1), the rate was found to be further depressed. The effect was ascribed to nitrate ions arising from the formation of urea nitrate. In the same way, urea depressed the rate of the zeroth-order nitration of mesitylene in sulpholan. ... 

Solutions of dinitrogen tetroxide (the mixed anhydride of nitric and nitrous acids) in sulphuric acid are nitrating agents ( 4.3.2), and there is no doubt that the effective reagent is the nitronium ion. Its formation has been demonstrated by Raman spectroscopy and by cryoscopy ... 

In aqueous solutions of sulphuric (< 50%) and perchloric acid (< 45 %) nitrous acid is present predominantly in the molecular form, although some dehydration to dinitrogen trioxide does occur.In solutions contairdng more than 60 % and 65 % of perchloric and sulphuric acid respectively, the stoichiometric concentration of nitrous acid is present entirely as the nitrosonium ion (see the discussion of dinitrogen trioxide 4.1). Evidence for the formation of this ion comes from the occurrence of an absorption band in the Raman spectrum almost identical with the relevant absorption observed in crystalline nitrosonium perchlorate. Under conditions in which molecular nitrous... 

The more powerful anticatalysis of nitration which is found with high concentrations of nitrous acid, and with all concentrations when water is present, is attributed to the formation of dinitrogen trioxide. Heterolysis of dinitrogen trioxide could give nitrosonium and nitrite ions 2N2O4 + HjO N2O3 + 2HNO3. 

In contrast to its effect upon the general mechanism of nitration by the nitronium ion, nitrous acid catalyses the nitration of phenol, aniline, and related compounds. Some of these compounds are oxidised under the conditions of reaction and the consequent formation of more nitrous acids leads to autocatalysis. 

Figure 22 5 shows what happens when a typical primary alkylamine reacts with nitrous acid Because nitrogen free products result from the formation and decomposition of diazonium ions these reactions are often referred to as deamination reactions Alkyl... 

A photochemical partial synthesis of aldosterone (19) made the hormone available on an industrial scale for the first time (114). Corticosterone acetate (51 acetate) is treated with nitrosyl chloride in pyridine at 20°C to yield the 11-nitrite (115). Irradiation of (115) leads to rearrangement with formation of the C g-oxime (116). Removal of the oxime residue with nitrous acid furnishes aldosterone (19) in excellent yield. 

In a polluted or urban atmosphere, O formation by the CH oxidation mechanism is overshadowed by the oxidation of other VOCs. Seed OH can be produced from reactions 4 and 5, but the photodisassociation of carbonyls and nitrous acid [7782-77-6] HNO2, (formed from the reaction of OH + NO and other reactions) are also important sources of OH ia polluted environments. An imperfect, but useful, measure of the rate of O formation by VOC oxidation is the rate of the initial OH-VOC reaction, shown ia Table 4 relative to the OH-CH rate for some commonly occurring VOCs. Also given are the median VOC concentrations. Shown for comparison are the relative reaction rates for two VOC species that are emitted by vegetation isoprene and a-piuene. In general, internally bonded olefins are the most reactive, followed ia decreasiag order by terminally bonded olefins, multi alkyl aromatics, monoalkyl aromatics, C and higher paraffins, C2—C paraffins, benzene, acetylene, and ethane. 

Nitrous acid or nitrite salts may be used to catalyze the nitration of easily nitratable aromatic hydrocarbons, eg, phenol or phenoHc ethers. It has been suggested that a nitrosonium ion (NO + ) attacks the aromatic, resulting initially in the formation of a nitro so aromatic compound (13). Oxidation of the nitro so aromatic then occurs ... 

Special reactions of hydrazides and azides are illustrated by the conversion of the hydrazide (205) into the azide (206) by nitrous acid (60JOC1950) and thence into the urethane (207) by ethanol (64FES(19)105Q) the conversion of the same azide (206) into the N-alkylamide (208) by ethylamine the formation of the hydrazone (209) from acetaldehyde and the hydrazide (205) and the IV-acylation of the hydrazide (205) to give, for example, the formylhydrazide (210) (65FES(20)259). It is evident that there is an isocyanate intermediate between (206) and (207) such compounds have been isolated sometimes, e.g. (211). Several of the above reactions are involved in some Curtius degradations. 

It was also found that bromonitrophenylmethane (375) reacted with sodium aryl-methanenitronate (374) in DMSO to give the isoxazoline iV-oxide (369) in 60% yield. Both reactions probably involved the formation of a vicinal dinitroethane derivative (376), which lost nitrous acid to give cfs-a-nitrostilbene (368). As mentioned, the reaction of (368) with (374) gave the isoxazoline iV-oxide (369). 

The most convenient route to S-nitrosothiol formation is the nitrosation of thiols by nitrous acid (Eq. 9.13). 

The mechanism is presumed to involve a pathway related to those proposed for other base-catalyzed reactions of isocyanoacetates with Michael acceptors. Thus base-induced formation of enolate 9 is followed by Michael addition to the nitroalkene and cyclization of nitronate 10 to furnish 11 after protonation. Loss of nitrous acid and aromatization affords pyrrole ester 12. 

In 1896, Graebe and Ullman reported the formation of carbazole (5) by reacting 2-aminodiphenylamine (3) with nitrous acid, followed by the thermolysis of the benzotriazole 4 which resulted. ... 

The rearrangement has been extended to other 4-substituted benzofuroxans of type 61, giving 62 i30-i32. although in no ease to date has the benzofuroxan been isolated, they are presumed intermediates in the formation of 63 and 64 from 5-dimethylaminobenzo-furoxan with 2,4-dinitrobenzenediazonium chloride and nitrous acid, respectively, and of 66 from 6, 68 from 67,and 70 from 69.132... 

The nitrosation of primary aromatic amines 1 with nitrous acid 2 and a subsequent dehydration step lead to the formation of diazonium ions 3. The unstable nitrous acid can for example be prepared by reaction of sodium nitrite with aqueous hydrochloric acid. 

The reaction of nitrous acid with the amino group of the /3-amino alcohol—e.g. 1-aminomethyl-cyclopentanol 1—leads to formation of the nitrosamine 4, from which, through protonation and subsequent loss of water, a diazonium ion species 5 is formed " —similar to a diazotization reaction ... 

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