Nitrite ion in aqueous solution

The coordination of Cd2+ by nitrite ion in aqueous solution has been studied by Raman spectroscopy,644 and cumulative formation constants have been derived (j81-j84 = 61.6, 993, 2390, 1899). Bidentate O chelation is postulated, except in the third and fourth complexes where unidentate nitrite is also present. This is in contrast to Zn, which forms Zn(N02)2 as its highest complex in aqueous solution. 

Table 2 Main reactions induced on organic compounds by excitation of nitrite ions in aqueous solution...

NH4, N2, and sulfate as a function of time resulting from the reaction of sulfite and nitrite ions in aqueous solutions was calculated at various conditions (Figures 1-6). A CHEMK software package developed by Systems Applications, Inc., of San Rafael, California, was used for this computation. Three different initial S02 and N0X concentrations were considered (in ppm) ... 

Nitrogen.—Oxoanions. Peroxonitrite ion reacts with the nucleophiles cyanide, iodide, or thiocyanate in alkaline solution. These reactions involve an associative mechanism for oxygen atom transfer to the nucleophile, to leave nitrite ion. In aqueous solution the A -hydroxohydroxylamine-A -sulphonate anion (5) decomposes to nitrous oxide and sulphate. In the pH range 6—10 the rate law is... 

Principally the same, but chemically simpler, sequence was used to prepare arylnitro anion-radicals from arylamines, in high yields. For instance, aqueous sodium nitrite solution was added to a mixture of ascorbic acid and sodium 3,5-dibromo-4-aminobenzenesulfonate in water. After addition of aqueous sodium hydroxide solution, the cation-radical of sodium 3,5-dibromo-4-nitro-benzenesulfonate was formed in the solution. The latter was completely characterized by its ESR spectrum. Double functions of the nitrite and ascorbic acid in the reaction should be underlined. Nitrite takes part in diazotization of the starting amine and trapping of the phenyl a-radical formed after one-electron reduction of the intermediary diazo compound. Ascorbic acid produces acidity to the reaction solution (needed for diazotization) and plays the role of a reductant when the medium becomes alkaline. The method described was proposed for ESR analytical determination of nitrite ions in water solutions (Lagercrantz 1998). 

Iron(II) sulfate is a reducing agent. In an aqueous solution, it reduces nitrate and nitrite ions forming a brown ring of Fe(N0)S04. This reaction is applied for qualitative detection of nitrate and nitrite ion in the solution. 

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. 

A somewhat similar result is found with the reaction between nitrite and iodide ions in aqueous solution. Here, too, the NO and 1 ions react most efficiently when screened by hydrions and the rate is proportional to [H+jpIO jEH+][ ], that is to [HNOgjEHI]. 

Fig. 19.5. Infrared absorption of common inorganic ions in aqueous solution. The molar absorptivity ( ) = absorbance/fmolarity x path length, in cm). A shoulder is indicated by sh. Notes (1) Bands due to solvated SOj are also usually present. (2) SO " is readily oxidized in aqueous solution to SO ". Absorption at 1105 cm is due to both v, of SOf" and vj of SOj". (3) Sulfur is precipitated at pH < 5. (4) Bands for more acidic forms are not included. Hydrolyzed to orthophosphate by boiling at low pH. (5) Concentrated solutions show band broadening, together with the appearance of a very weak band at 1045 cm" .(6)The 1330 cm band appears as a shoulder on the side of the 1230 cm" band. Nitrites decompose at pH < 5. (7) Concentrated solutions show a very weak band at 1060cm". (8) An additional band observed near 1700 cm" not included in this figure. (Goulden and Manning, 1967.)...

The NO2 radicals obtained from nitrite ions in acidic solution add to olefins regioselectively. The resulting radical is oxidized in situ by CAN to provide nitroolefins, even labile ones, in high yield and short reaction times.32 The second reaction in Fig. 5 shows another preparation by the addition of nitryl iodide, from potassium nitrite and iodine, followed by a base-induced elimination of hydrogen iodide. A radical mechanism is probably not involved. This mild one-pot method, a valuable alternative to other published techniques, is accomplished in a non-aqueous medium and gives good yields and regioselectivities even with sterically hindered substrates. 

The Blomstrand-J0rgensen model suggested that the trisamine also should give two ions in aqueous solution, while the Werner model suggested that both the three amines and the three nitrite ions should be strongly bonded to the metal. This implied that the complex forms one molecular unit. And indeed, the electrical conductivity of the aqueous solution was found to be negligible. Werner s model was clearly the better ... 

Of course, in aqueous solution the reactants and the products exist wholly or partly in their ionized forms the acid, nitrite, and salt exist as H+X , Na+N02, and Na+X , while the diazonium salts are practically completely ionized and the amine is in equilibrium with the corresponding ammonium ion, Ar—NH3. The question of which of these various species are involved in the substitution proper will be dealt with in Chapter 3. Although it is generally desirable to introduce ionized forms into equations, this is inappropriate for the overall equation for the diazotization process, as will become apparent in the discussion of the reaction mechanism (Ch. 3) and from the following remarks. 

The UV absorption spectra of sodium nitrite in aqueous solutions of sulfuric and perchloric acids were recorded by Seel and Winkler (1960) and by Bayliss et al. (1963). The absorption band at 250 nm is due either to the nitrosoacidium ion or to the nitrosyl ion. From the absorbancy of this band the equilibrium concentrations of HNO2 and NO or H20 —NO were calculated over the acid concentration ranges 0-100% H2S04 (by weight) and 0-72% HC104 (by weight). For both solvent systems the concentrations determined for the two (or three) equilibrium species correlate with the acidity function HR. This acidity function is defined for protonation-dehydration processes, and it is usually measured using triarylcarbinol indicators in the equilibrium shown in Scheme 3-15 (see Deno et al., 1955 Cox and Yates, 1983). 

Cyanide and thiocyanate anions in aqueous solution can be determined as cyanogen bromide after reaction with bromine [686]. The thiocyanate anion can be quantitatively determined in the presence of cyanide by adding an excess of formaldehyde solution to the sample, which converts the cyanide ion to the unreactive cyanohydrin. The detection limits for the cyanide and thiocyanate anions were less than 0.01 ppm with an electron-capture detector. Iodine in acid solution reacts with acetone to form monoiodoacetone, which can be detected at high sensitivity with an electron-capture detector [687]. The reaction is specific for iodine, iodide being determined after oxidation with iodate. The nitrate anion can be determined in aqueous solution after conversion to nitrobenzene by reaction with benzene in the presence of sulfuric acid [688,689]. The detection limit for the nitrate anion was less than 0.1 ppm. The nitrite anion can be determined after oxidation to nitrate with potassium permanganate. Nitrite can be determined directly by alkylation with an alkaline solution of pentafluorobenzyl bromide [690]. The yield of derivative was about 80t.with a detection limit of 0.46 ng in 0.1 ml of aqueous sample. Pentafluorobenzyl p-toluenesulfonate has been used to derivatize carboxylate and phenolate anions and to simultaneously derivatize bromide, iodide, cyanide, thiocyanate, nitrite, nitrate and sulfide in a two-phase system using tetrapentylammonium cWoride as a phase transfer catalyst [691]. Detection limits wer Hi the ppm range. 

In addition to the aqueous method for diazotization in aqueous solution, diazonium ions can be generated in organic solvents by reaction with alkyl nitrites. 

The NO reduction of the Cu(II) complex Cu(dmp)2(H20)2+ (dmp = 2,9-dimethyl-l,10-phenanthroline) to give Cu(dmp)2 plus nitrite ion (Eq. (20)) has been studied in aqueous solution and various mixed solvents (42a). The reduction potential for Cu(dmp)2(H20)2+ (0.58 V vs. NHE in water) (48) is substantially more positive than those for most cupric complexes owing to steric repulsion between the 2,9-methyl substituents that provide a bias toward the tetrahedral coordination of Cu(I). The less crowded bis(l,10-phenanthroline) complex Cu(phen)2(H20)2+ is a weaker oxidant (0.18 V) (48). 

More than thirty years ago Seel and Winkler74 as well as Bayliss and coworkers75 investigated the UV absorption spectra of sodium nitrite in aqueous solutions of sulfuric and perchloric acids (equation 18, for H2SO4). The absorption band found at 250 nm is due either to the nitrosoacidium ion or to the nitrosyl ion. From the absorbency of... 

When thiocyanate ions are added to nitrous acid in water, a pink colouration develops which is believed to be due to the formation of nitrosyl thiocyanate (equation 34), which is too unstable to be isolated but which can be used as a nitrosating agent in aqueous solution. Because the equilibrium constant for ONSCN formation81 is quite large (30 dm6mol 2) at 25 °C, thiocyanate ion is an excellent catalyst for aqueous electrophilic nitrosation. The well established82 series is Cl- < Br < SCN < (NH2)2CS. Thiocyanate ion is also a sufficiently powerful nucleophile to react in acid solution with nitrosamines in a denitrosation process (equation 35), which can only be driven to the right if the nitrosyl thiocyanate is removed by, e.g., reaction with a nitrite trap such as hydrazoic acid. 

Chan, W.F. and Larson, R.A. Mechanistrrs and products of ozonolysis of aniline in aqueous solution containing nitrite ion. Water Res., 25(12) 1549-1544, 1991a. 

The radical-anions of aliphatic nitrocompounds are detectable in aqueous solution as transient intermediates formed during continuous electrolysis in the cavity of the esr spectrometer [4], Decay of the species occurs by protonation and then further reactions. 2-Methyl-2-nitropropane has no acidic hydrogens so that it can be examined in aqueous alkaline solution where the radical-anion is not protonated. Over the pH range 9-11, this radical-anion decays by a first order process with k = 0.8 0.1 s at 26 C. Decay results from cleavage of the carbon-nitrogen bond to give a carbon centred radical and nitrite ion. Ultimately, the di-(ferr,-butyI)nitrone radical is formed in follow-up reactions [5],... 

Trace amounts of the nitrite ion (NO ) are indicative of the extent of pollution and eutrophication. The multitude of methods that can measure nitrite ion concentrations, such as colorimetry, chemiluminescence or fluorimetry, are not capable of detecting subnanomole amounts of nitrite. These also suffer from interference problems. A highly sensitive and selective method for the determination of low concentrations of nitrite in aqueous solutions using surface-enhanced resonance Raman (SERRS) has been developed (13) (see Section 3.3). 

Short-lived iodine fission products have also been separated by a similar method. In this case, an oxidant such as nitrite ion in acidic aqueous solution has been used (50,255) the iodine extracted into carbon tetrachloride, and then back-extracted into an aqueous solution containing sodium hydrosulphite (50). 

As part of the work on model heme FeNO complexes, mechanistic studies on the reversible binding of nitric oxide to metmyoglobin and water soluble Fe, Co and Fe porphyrin complexes in aqueous solution, ligand-promoted rapid NO or NO2 dissociation from Fe porphyrins, reductive nitrosylation of water-soluble iron porphyrins, activation of nitrite ions to carry out O-atom transfer by Fe porphyrins, demonstration of the role of scission of the proximal histidine-iron bond in the activation of soluble guanylyl cyclase through metalloporphyrin substitution studies, reactions of peroxynitrite with iron porphyrins, and the first observation of photoinduced nitrosyl linkage isomers of FeNO heme complexes have been reported. 

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