Anions in aqueous solution

The diversity of chemical reactions is immense. To make sense of this vast expanse of chemistry, we need a system for grouping chemical reactions into categories. The reactions within each category should share some characteristics or follow a common theme. One relatively simple category is precipitation reactions, in which cations and anions in aqueous solution combine to form neutral insoluble solids. 

The number of solute particles present in a given amount of solvent causes the temperature changes described by Equations and. When an ionic salt dissolves in water, each mole of salt produces two or more moles of ions. A dilute solution of sodium chloride (NaCl), for example, contains two moles of ions for every mole of NaCl—one mole of Na cations and one mole of Cl anions. The proper application of Equations and takes this into account by viewing as the toto/number of moles of particles per kilogram of solvent. When this is done, however, the predicted values of A Tf or A 7ti are higher than experimental values. This is because some of the cations and anions in aqueous solutions form ion pairs, reducing the total number of solute particles. 

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. 

J.M. Lu, J. Geimer, S. Naumov and D. Beckert, A Fourier transform EPR study of uracil and thymine radical anions in aqueous solution, Phys. Chem. Chem. Phys., 2001, 3, 952. 

Figure 12.1 Iodide anion in aqueous solution undergoes an equilibrium reaction process to form the reactive H20I+ species.

Figure 12.3 The strong oxidant chloramine-T can react with iodide anion in aqueous solution to form a highly reactive mixed halogen species. 125IC1 then can modify tyrosine and histidine groups in proteins to form radiolabeled products.

Oxidation of the BioHio2 anion in aqueous solution either by Fe3+ or Ce4+ joins two of the Bi0 clusters to the con/uncto-icosaborate B2oH182 (see Section 2.1.5.8). 

Photolysis of peroxydisulphate anions in aqueous solution produces the S04 sulphate radical. This radical reacts with phosphoric acid and its anions to generate phosphorus-containing radicals which can be trapped by such compounds as fumaric acid.31... 

Solvolysis studies of meta- and para-substituted phenyl phosphates (240) in anhydrous Bu OH and in Am OH have revealed that generally reactions of dianions are much faster in alcohols than in water. For example, the dianion of p-nitrophenyl phosphate (240 X = 4-NO2) reacts 7500- and 8750-fold faster in Bu OH and Am OH, respectively, than in water." The results of a theoretical study of the reactivity of phosphate monoester anions in aqueous solution do not support the generally accepted view that Brpnsted coefficients fhg = —1.23 and jSnuc = 0.13 determined more than 30 years ago for the uncatalysed reaction of water and a monophosphate dianion (241) represent conclusive evidence for the dissociative mechanism. It is suggested that, instead, the observed LFERs could correspond to a late transition state in the associative mechanism." ... 

The strong hydration of halide ions in water is partly due to outer-sphere effects. Oxo anions in aqueous solution may complex with outer-sphere water molecules as in the hydrated chromate and permanganate ions ... 

Copper(I) sulfide reacts with polysulfide anions in aqueous solutions forming soluble copper polysulfides. 

Mercury(I) nitrate undergoes double decomposition reactions with anions in aqueous solution, forming corresponding mercury(l) salts. With potassium iodide and sodium bromide, yellow mercury(l) iodide and white mercury(I) bromide precipitate, respectively. Similarly, mercury(l) nitrate in acid medium reacts with dilute sulfuric acid to form mercury(1) sulfate ... 

Simple one-electron reduction of manganese tetraoxo anions in aqueous solution is observed only under very alkaline conditions. Hydroxide ion concentrations greater than 0.4 and 10 M are required... 

Waygood, S. J., and W. J. McElroy, Spectroscopy and Decay Kinetics of the Sulfite Radical Anion in Aqueous Solution, J. Chem. Soc. Faraday Trans., 88, 1525-1530 (1992). 

Decomposition Half-Lives for Sodium Trimeta- and Tetrametaphosphate Anions in Aqueous Solution at 60°C as a Function of pH... 

These examples are sufficient to form the basis of the discussion of the nature of cations and anions in aqueous solutions. In aqueous solution, ions are stabilized by their interaction with the solvent they become h>drated and this slate is indicated in equations by the (a< ) symbolism. This is a broad generalization and is amplified by further discussions in the next sections and in the remainder of the book. 

Simos, T. E. (Ed.), Structure and Dynamics of Composite Anions in Aqueous Solution , American Institute of Physics (AIP) New York, 2007. 

SiMouO ]4-.134 The structure of the heteropoly blue species (four-electron-reduced PM012O40]3-) formed in the molybdenum blue determination of phosphorus has been reported135 and a review of molybdate heteropoly blues has appeared.130 A stability index of polyanion structures has been discussed.137 The presence of two PMo, anions in aqueous solutions of molybdate and phosphate has been demonstrated by 31P NMR.138 Solid state NMR (nonspinning and MAS techniques) has been used for characterization of heteropolyanions.139 Molybdenum-95 NMR spectra of some polymolybdates have been reported.140... 

Neta, P., and D. Meisel, Substituent effects of nitroaromatic radical anions in aqueous solution , J. Phys. Chem., 80, 519-524(1976). 

The enthalpy and entropy of complex formation between Zn11 and picolinate and dipicolinate anions in aqueous solution have been determined by calorimetry and from formation constant data. The greater stability of the dipicolinate complex compared to the picolinate complex reflects an entropy effect, and Ais actually less favourable. These anions are well known to have a low basicity to H+ compared to their complexing ability to metals. In the present case, this probably reflects the coplanarity of the carboxylate anions and the pyridine ring, so that the oxygen atoms are in a favourable position to coordinate.800... 

Manifestations of nuclei tunneling in chemical reactions in gaseous, liquid, and solid phases are consecutively considered in Sects. 4.2-4.5. Also discussed in this chapter are (1) manifestations of nuclear tunneling in the vibrational spectra of ammonia-type molecules (Sect. 4.6), (2) electron tunneling in gas-phase chemical reactions of atom transfer (the so-called "harpoon reactions, Sect. 4.2), and (3) tunneling of hydrated electrons in the reactions of their recombination with some inorganic anions in aqueous solutions (Sect. 4.4). 

There are also certain data on electron tunneling in electron transfer reactions in liquids. The ideas about electron tunneling have been used by Anbar and Hart [75] to interpret the anomalously large rate constants for the diffusion controlled reactions of hydrated electrons with some inorganic anions in aqueous solution. Table 5 represents the data on the largest values of the rate constants, ke, observed for the reactions of eaq with various inorganic anions and cations. Theoretical diffusion rate constants, kA, for... 

Van der Zee J, Dubbelman TMAR, Van SteveninckJ (1987) The role of hydroxyl radicals in the degradation of DNA by ozone. Free Rad Res Commun 2 279-284 Vieira AJSC,Telo JP (1997) EPR detection of oxygen radical anion in aqueous solution at room temperature. Redox Rep 3 349-350... 

Naumov S, Beckert D (2002) Reply to the Comment on A Fourier transform EPR study of uracil and thymine radical anions in aqueous solution)/ by DM Close. Phys Chem Chem Phys 4 45 Naumov S, Barthel A, Reinhold J, Dietz F, Geimer J, Beckert D (2000) Calculation of spin densities of radicals of pyrimidine-type bases by density functional theory. Influence of solvent and comparison with EPR results. Phys Chem Chem Phys 2 4207-4211 Naumov S, Hildenbrand K, von Sonntag C (2001) Tautomers of the N-centered radical generated by reaction of SO4 - with N(1)substituted cytosines in aqueous solution. Calculation of isotropic hyperfine coupling constants by a density functional method. J Chem Soc Perkin Trans 2 1648-1653... 

Niehaus H, Hildenbrand K (2000) Continuous-flow and spin-trapping EPR studies on the reactions of cytidine induced by the sulfate radical-anion in aqueous solution. Evidence for an intermediate radical cation. J Chem Soc Perkin Trans 2 947-952 Niles JC, Burney S, Singh SP, Wishnok JS, Tannenbaum SR (1999) Peroxynitrie reaction products of 3, 5 -di-0-acetyl-8-oxo-7,8-dihydro-2 -deoxyguanosine. Proc Natl Acad Sci USA 96 11729-11734... 

Burkitbaev, M. (2003) Radiation-stimulated oxidation reactions of oxo anions in aqueous solutions. High Energy Chemistry, 37(4), 216-19. 

Consider a hydrated cation M and a ligand L (which may be neutral or anionic) in aqueous solution (for clarity and simplicity, charges are not specified). If the coordination number of M is 6, and if L is unidentate, we can form complexes ML (n = 1-6). The equilibria can be written in two ways ... 

Amendola, V., Fabbrizzi, L., Mangano, C., Pallavicini, P., Zema, M., A di-copper(II) bis tren cage with thiophene spacers as receptor for anions in aqueous solution. Inorg. Chim. Acta 2002, 337, 70-74. 

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