Protonated anions

Protonated Anions. Ions such as HSOy are recommended to be named hydrogensulfate with the two words written as one following the usual practice for polyatomic anions. However, in the Nomenclature of Organic Chemistry, 1979 edition, hydrogen is used as a separate word this practice is followed in this Handbook. 

A surprising exception has been reported with evidence for a cleavage reaction in the case of divinyl sulphone. In non-aqueous and slightly acidic media, the behaviour of a., ji-unsaturated aromatic sulphones is also complex (see Table 7) since the cleavage and the saturation may compete. Strongly electrophilic double bonds undergo Michael additions in aprotic solvents by slowly protonated anions. Transfer of labile hydrogen may also lead to unactivated bases. It is noteworthy that in numerous cases (Table 6) the saturation is the preferred route. 

The chemical composition of anodic aluminas, with special emphasis on the depth-dependent incorporation of electrolyte species (protons, anions, etc.), has been extensively studied. 

If a hydrolyzed metal ion is adsorbed, its OH" will be included in the proton balance similarly, in case of adsorption of protonated anions, their H+ will be included in the proton balance. 

Adsorption of anions on oxides is usually accompanied by the uptake of protons (or the release of hydroxyl ions). The ratio between the number of protons that are coadsorbed and the level of anion adsorption is not usually stoichiometric. Studies of adsorption of oxyanions on goethite as a function of pH appear to indicate that, provided only one adsorbed species is present, the proton anion ratio is related to the mode of adsorption (Rietra et al., 1999). It follows that oxyanions which adsorb with a similar proton/anion stoichiometry, have a similar adsorption mechanism. 

Most frequent are Py complexes in which the heptaphosphanortricyclane unit is retained. In the protonated anion [(Py)Pt(H)PPh3] [247], the platinum atom coordinates side-on to two lone pairs of two divalent P atoms. When the related Ni(CO) complex shown in Fig. lOh is protonated, the incoming proton is attached... 

The thymine anion is only a weak base = 6.9) [22]. This means that protonation of the anion may depend on the specific environment. The primary reduction product observed in the solid state in thymine derivatives is the C4-OH protonated anion [17]. This species exhibits significant spin density at C6 and 04. Here one must distinguish between two different situations. In single crystals of thymidine, the C4-OHp proton is out of the molecular plane which gives rise to an additional 33.1-MHz isotropic hyperfine coupling [31]. A similar situation is observed in single crystals of anhydrous thymine [32]. In 1-meThy, however, the C4—OHp proton is in the molecular plane. Consequently, the proton coupling is very small. 

The previous section outlined the typical e loss and e gain products observed in the nucleic acid bases in the solid state. These studies can be applied to the study of the radiation chemistry of DNA. The relevance of the study of model systems is shown by considering the following remarkable observations. Years ago, Ehrenberg et al. showed the EPR spectra of the 5,6-dihydrothymine-5-yl radical observed in thymine, thymidine, and DNA. The spectra are nearly identical [46]. The reduction product observed in cytosine monohydrate is the N3 protonated anion. In solution, this reduction product gives rise to a 1.4-mT EPR doublet. The same feature is present in irradiated DNA at 77 K. Likewise, the result of e loss in guanine bases is characterized by a broad EPR singlet. The same feature is also evident in the EPR spectrum of DNA irradiated and observed at 77 K. 

Anionic substituents that are considered are the salts of carboxylic acids, phosphoric acids, and sulfur acids. The salts of sulfur acids are chosen based on their low pKa values that allow these derivatives to remain un-protonated (anionic) throughout the pH range used in and experienced by pharmaceutical formulations. Figure 7 shows the chemical structures of the three different families of anionic CD derivatives... 

Thiosemicarbazide (tscH) (40a) exists in the two tautomeric forms shown in (41). It may coordinate either as a neutral or (by loss of a proton) anionic N—S bidentate. The nickel(II) complexes in particular of thiosemicarbazide and related ligands (40) have been studied in considerable detail. 

In the Rh (entry 37) or Pd thiaporphyrin derivatives (entry 47), the thia-pyrrole-tripyrrole macrocycle is not planar. Because the thiaporphyrin only carries one central proton, anions are required as axial ligands in its chelates to neutralize the latter. Pd(SDPDTP) (entry 47) does not have an anion. It has been formed by one-electron reduction from Pd(SDPDTP)Cl. An extra electron... 

Studying the ESPT of hydroxy aromatic sulfonates, Huppert and co-workers [40-44] suggested an alternative model based on the geminate proton-anion recombination, governed by diffusive motion. The analysis was carried out by using Debye-Smoluchowskii-type diffusion equations. Their ESPT studies in water-methanol mixtures showed that solvent effects in the dissociation rate coefficient are equal to the effects in the dissociation equilibrium constant [45], 4-Hydroxy-1-naphthalenesulphonate in a water-propanol mixture as the solvent system has been found to behave somewhat differently than water-methanol or water-ethanol media, with a possible role of a water dimer [46,47],... 

The polarographic behavior of aromatic carbonyl compounds at the dropping mercury electrode in aqueous SSE s is rather complex 130 In acid medium two one-electron waves are observed, corresponding to reduction of the protonated ketone (protonation makes the reduction easier, shifting the first wave towards less cathodic potentials with decreasing pH) and the protonated anion radical, respectively ... 

Cpe at the plateau of the first wave was reported to give the coupling product (the pinacol). At higher pH values (2-9) the pH-dependent first wave moves towards more cathodic potentials, finally merging with the pH-independent second wave. Cpe at the plateau of the combined two-electron wave gives the alcohol as product according to the mechanism outlined in Eqs. (67), (68) and (69). The protonated anion radical is now easier to reduce than the ketone, resulting in the two-electron transfer observed. 

It is clear that the ability of alcohols to protonate anionic reactive intermediates and their ability to coordinate to Sml2 (thus increasing the effective molarity and acidity of the proton donor) are factors that should be considered when planning reaction sequences using the reductant. 

The proton of HN203 is bound to a nitrogen atom according to 02N-NH-0. Addition of nitrite to an aqueous solution of HN203 shifts the dissociation equilibrium (246) to the left side and stabilizes the protonated anion. 

K. The three markers at the bottom are the positions of the Fremy Salt resonances, withyf = 2.0056 and = 2.0056. (B) to (E) are spectra used as benchmarks for deconvolution of the DNA spectrum. (B) One-electron oxidized guanine. (C) One-electron reduced cytosine (i.e. the protonated anion radical). (D) Thymine anion radical. (E) Composite spectrum of neutral sugar radicals. 

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