Anions, determination

W J Williams, Handbook of Anion Determinations, Butterworths, London, 1979, p 350... 

For carbanionic addition, the relative negative charge and the electron densities in the 1- and 3-position in the HOMO of the ambident allylic anion determine, in addition to steric effects, the regioselectivity of the hydroxyalkylation. According to the allopolarization principle13 the following generalizations can be made ... 

TBTO is a colorless liquid of low water solubility and low polarity. Its water solubility varies between <1.0 and >100 mg/L, depending on the pH, temperature, and presence of other anions. These other anions determine the speciation of tributyltin in natural waters. Thus, in sea water, TBT exists largely as hydroxide, chloride, and carbonate, the structures of which are given in Figure 8.5. At pH values below 7.0, the predominant forms are the chloride and the protonated hydroxide at pH8 they are the chloride, hydroxide, and carbonate and at pH values above 10 they are the hydroxide and the carbonate (EHC 116). 

Applications Electrochemical techniques, while lacking the wide elemental range and long linear response of some atomic and mass spectrometry technologies, offer a valuable alternative in a number of specific applications, and have particular advantages for direct speciation and anion determination. In ion chromatography, amperometric, potentiometric and conductometric detection is widely used [472], see also Section 4.4.2.5. 

Fig. 9 Honeycomb-like architectures formed on self-assembly of halide anions (which work as tridentate XB acceptors and sit at the networks nodes) with 1,4-DITFB (which works as bidentate donor and forms network sides) (A). The angles formed by the XBs around the halide anions determine the corrugation of the honeycomb architecture, a more planar arrangement around the halide anions (as is the case of the iodide anions in adduct l,4-DITFB/Me4P+r (B) with respect to the bromide anions in adduct l,4-DITFB/Ph4P+Br (C)) results in a less corrugated honeycomb architecture...

The differing nucleophilicity of acetate and trifluoroacetate anion determined the manner in which naphtho[l,8-/yt]-l,5-dithiocinc sulfoxide 127 rearranged on treatment with acetic and trifluoroacetic anhydrides. In both cases, the reaction proceeded through formation of a disulfonium dication 128, but the final products were different. When acetic anhydride was used, the reaction afforded the corresponding a-acetylsulfide 130, a normal product of the Pummerer rearrangement, while trifluoroacetic anhydride caused isomerization with formation of dithioacetal 132 (see Scheme 16) <1995HAC559>. 

Ion chromatography is used at the City of Lincoln, Nebraska, Water Treatment Plant Laboratory to analyze water samples taken from sampling sites in the distribution system around the city. The common anions determined by IC are not only nitrate, nitrite, fluoride, and sulfate, but also bromate. Bromate is found in the water because the Lincoln plant treats the water with ozone. Adding ozone to the water oxidizes any bromide to bromate. Bromate is regulated at 10 parts per billion (ppb) its concentration must be determined. 

Scheme 28 The templating anion determines the orientation of the threads in the pseudoro-taxane, which has important consequences for the solid-state structure of these assemblies...

In most ionic crystals, the anion is larger than the cation and, therefore, the packing of the anions determines the arrangement of ions in the crystal lattice. There are several possible arrangements for ionic crystals in which the anions are larger than cations, and cations and anions are present in equal molar amounts. For example. Figure 4.22 shows two different arrangements found in the structures of sodium chloride, NaCl, and cesium chloride, CsCl. 

Properties of radical-anions determined by pulse radiolysis in buffered aqueous... 

The anions determine the chemical properties of ionic liquids to a large extent. For example, the following ionic liquids, in which the cation is the same and the anions are not, behave totally different from one another ... 

In 1985, Ruzicka and Hansen established the principles behind flow injection optosensing [13-15], which has subsequently been used for making reaction-rate measurements [16], pH measurements by means of immobilized indicators [17,18], enzyme assays [19], solid-phase analyte preconcentration by sorbent extraction [20] and even anion determinations by catalysed reduction of a solid phase [21] —all these applications are discussed in Chapters 3 and 4. Incorporation of a gas-diffusion membrane in this type of sensor results in substantially improved sensitivity (through preconcentration) and selectivity (through removal of non-volatile interferents). The first model sensor of this type was developed for the determination of ammonium [13] and later refined by Hansen et al. [22,23] for successful application to clinical samples. 

In Table 3 the total energy through second-order and the second-order correlation energy component for the ground state of the fluoride anion determined with a sequence of basis sets designed for the neutral F atom are presented. Values of A [p/o](F [F])[2 p and AE2 F [N]) 2 results presented in Table 3 should be compared with... 

In Table 7 the total energy through second-order and the second-order correlation energy component for the ground state of the fluoride anion determined with a sequence of basis sets designed for the neutral F atom. 

A physical model and a theory have been proposed [72], which might be helpful in comparative studies on electrocompres-sive behavior of electrodeposited chloride, bromide, and iodide monolayers on the Au(lll) electrode. The theoretical results were in good agreement with the experimental data, which evidence that the adatom-adatom interactions (especially repulsive ones) and electrosorption valency of halide anions determine the compressibility within halide adlayers. Also, Lipkowski et al. have discussed various aspects of adsorption of halide anions on Au(lll) in a review paper [36]. From this paper, we have taken quantitative data concerning adsorption of halide anions on Au(lll) (cf Fig. 3). 

Hydration Structure Parameters For Composite Anions Determined By QMCF MD Simulations ... 

Turning from a consideration of relative phase stability as it is anion-determined, let us now examine the much stronger cation dependency. Why is it NdS is collapsed under room conditions, but SmS expanded The answer lies clearly in the position of the ff band, as it is found in Fig. la (or lb). 

The type of ligand (neutral molecules or anions) determines the charge of the transition metal complex and hence the conditions such as support nature and pH range, for which ion exchange can occur. 

Isse, A.A. and Gennaro, A. (2004) Homogeneous reduction of haloacetonitriles by electrogenerated aromatic radical anions Determination of the reduction potential of CH2CN. J. Phys. Chem. A 108,4180 1186. 

Assumed similar to that of the corresponding anion. Determined in H2SO4. 

Of course, the ratio of the proton affinities of the monomer u to tlwse of the anion determines the nature and position of the equilibrium. 

It has been shown experimentally that relationship (4) is maintained whether the internal or external pH is varied in order to change A pH. Relationship (4) could also be derived by assuming that the free acid is completely permeable and the anion impermeable to the membrane. At equilibrium the concentration of free acid should be equal inside and out, and the amount of internal and external anions determined by pK and ApH. 

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