Anions, Table

The redox potential and the reactivity of this oxidation state depend strongly upon the anion (Table 11). Strong complexes are formed with SO ". Even in perchloric acid, hydrolysis and polymerisation greatly complicate kinetics. The co-ordination number of Ce(lV) in solution is not established . 

Tables 15 and 16 show the absorption maxima of some metal complexes of benzothiazolyl-substituted formazans 230 and 231.283 The wavelengths are metal ion dependent, making formazans useful reagents for the identification of specific metal ions or the simultaneous determination of two ions. The wavelengths are much longer than those of the formazan anion (Table 14). The general trend for electron-rich substituents is toward a larger shift this is to be expected as it tends to enhance the aromatic character of the ring and increase the covalent character of the metal — nitrogen bond. The sharpness of the absorption band has been attributed to coordination to the heterocyclic nitrogen as in 232.57S...

The effectiveness of zinc is related to its associated anion (Table 7) the chloride, acetate, or benzoate salts were the most effective. The maximum effectiveness of the metal would be expected if the exchange reaction with the pigment surface was... 

The group of the chalcogens sulfur, selenium and tellurium is a typical triad of the more electronegative nonmetals with relatively high-ionization energies, relatively strong element-element bonds and a clear tendency to form mono-and polyatomic anions (Table 1). 

The reductive dehalogenation of haloalkanes has also been achieved in high yield using polymer supported hydridoiron tetracarbonyl anion (Table 11.15). In reactions where the structure of the alkyl group is such that anionic cleavage is not favoured, carbonylation of the intermediate alkyl(hydrido)iron complex produces an aldehyde (see Chapter 8) [3]. 

The barriers to acetyl group rotation in 84a to d are at least as high as in the acetylacetonate anion (Table 18), indicating a considerable delocalization of negative charge into Ac—Q—Ac. As mentioned later (Table 19), the twist angle in 84a is 73°. ... 

The removal of fertilizer N in the crop as NH4+ does not lead to acidification. Hydrolysis of urea fertilizer—by far the main form of N fertilizer used in wetland rice, together with ammonium bicarbonate in some countries—consumes 1 mol of H+ per mol of NH4+ formed (Table 7.1, Process 1). So although absorption of N as NH4+ leads to a net export of H+ from the roots to balance the resulting excess intake of cations over anions (Table 7.1, Process 5), this acidity is matched by the H+ consumed in urea hydrolysis. Likewise there is no net generation of acidity as a result of NH3 volatilization, although 1 mol of H+ is left behind per mol of NH4+ converted to NH3 (Table 7.1, Process 3). 

Primary, secondary and tertiary aliphatic amines are efficiently converted to nitro compounds in 80-90 % yield with dimethyldioxirane, a reagent prepared from the reaction of oxone (2KHSO5-KHSO4-K2SO4) with buffered acetone. Dimethyldioxirane (DMDO) has been used for the synthesis of 1,3,5,7-tetranitroadamantane (71) from the corresponding tetraamine as the tetrahydrochloride salt (70) and is an improvement over the initial synthesis using permanganate anion (Table 1.7). ° Oxone is able to directly convert some aromatic amines into nitro compounds. 

NUCLEOPHILIC REACTIONS INVOLVING ENOLATE ANIONS Table 10.1 Keto-enoL equiLibria... 

However, several years later Priester and coworkers revised the interpretation of the IR spectra of polylithiated acetylenes in terms of propargylide and allenic anions (Table 11) ". They divided the compounds into two categories those that can directly form lithioacetyUdes (the terminal acetylenes) and those that must undergo hydrogen or alkyl shifts to form acetylides (the internal acetylenes). 

As well as increasing anion nucleophilicity, crown or cryptand complexation can enhance the basicity of the anion. Table 3 exemplifies this effect with 1-bromooctane where base-promoted elimination to 1-octene competes with nucleophilic substitution. Being small and poorly solvated, naked fluoride is a strong and hard base which causes, in the case of certain substrates (e.g. Scheme 6), the elimination product to predominate. As the naked anions increase in size they display less basic characteristics but retain high nucleophilic reactivity (74JA2250). 

Similar probes can be used in the study of proteins that do not require a metal ion. One example has been the study of lysozyme, where the probes used have been the lanthanide(III) cations and various anions (Table II). Additionally, for X-ray crystallographic purposes, a whole range of metal atoms has been incorporated into proteins. For these X-ray studies, it is only necessary that the metal atom has high atomic weight and that major structural perturbations are not caused. 

The ESR data for several silaacenaphthene and silaphenalene radical anions (Table VI) obtained by electrolytic reduction (101), are similar to the results for trimethylsilyl-substituted naphthalenes (Table V) (49). The polarographic reduction potentials were 0.2-0.4 volt more positive than that of naphthalene (101). Similarly, some silaphenalene derivatives of the type X[R = H(R ,R = H,H H,Me Me,Me) and R = Ph R1 = R2 = Me] were shown by polarographic analysis to reduce more easily than silylnaphthalene or naphthalene and the unassigned ESR spectra of the radical anions were reported (99). 

Large anions, such as I- and CIO4, have a relatively weak tendency to accept hydrogen bonds. However, they are highly polarizable and interact to a fair extent by dispersion forces (London forces) with the molecules of aprotic solvents, which are also considerably polarizable. Thus, for large anions, the solvation energies in protic solvents (water, alcohols) and those in dipolar aprotic solvents (AN, DMF, DMSO) are not as different as in the case of small anions (Table 2.4). 

Figure 16 The structure of [TeMo6024]6 ( Anderson ) anion Table 9 Anderson and Related Heteropolyanions...

The same study shows that with the complex of A W-dimethyl-o-toluidine (38), the selectivity depends on time, temperature and the nature of the anion (Table 4 and equation 34).87 Again, equilibration occurs with the tertiary nitrile-stabilized anion, favoring the C-4 substitution product, while lithioacetonitrile favors addition at C-3. The 2-methyl-1,3-dithianyl anion gives precisely the same product mixture at -78 °C and at -30 C there is no evidence for equilibration with this anion. 

Introduction of room-temperature ionic liquids (RTIL) as electrochemical media promises to enhance the utility of fuel-cell-type sensors (Buzzeo et al., 2004). These highly versatile solvents have nearly ideal properties for the realization of fuelcell-type amperometric sensors. Their electrochemical window extends up to 5 V and they have near-zero vapor pressure. There are typically two cations used in RTIL V-dialkyl immidazolium and A-alkyl pyridinium cations. Their properties are controlled mostly by the anion (Table 7.4). The lower diffusion coefficient and lower solubility for some species is offset by the possibility of operation at higher temperatures. 

Following the recommendation of Reinhoudt,23 in almost the majority of cases, nitrophenyl alkyl ethers were used as diluents for the extraction tests by the Cadarache group, because they are able to dissolve calixarenes at relatively high concentration. Moreover, the basicity as well the dielectric constant of these diluents improves cation extraction by better solvation of the associated nitrate anions (Table 4.3). 

Far from third-phase formation, Kanellakopulos et al. (118) showed in an earlier study that the extraction behavior of given electrolytes with the same cation is primarily influenced by the solvation properties of the associated anions. They found that the electrolyte phase distribution can be explained by single ion solvation, by comparing the equilibrium constants for the extraction of acids by undiluted TBP with the free energies of transfer for the anions (Table 7.3). 

Tables IV through IX summarize the data that are currently available on the rates of bimolecular substitution and dehydrohalogenation reactions between sulfur nucleophiles and halogenated aliphatic substrates in aqueous solution (i.e., either measured in water or extrapolated to water from a non-aqueous or partially aqueous solvent). The sulfrir nucleophiles considered in these tables are HS-, S2-, S42-, S52- (Table IV), S2032 (Tables V and VIII), SO32-, HSO3 (Table VI), thiolate anions (Tables VII, VIII, and IX), thiols, thioethers, and thioadds (Table VII).

The onset of decomposition of arylpentazoles is difficult to determine. Even freshly prepared samples can contain impurities of the corresponding azides, which increase during heating. Therefore the decomposition temperature cannot be determined exactly. The most stable pentazoles include />-dimethylaminophenylpentazole and the />-oxophenylpentazole anion (Table 8). The experimentally determined activation energies are not in total agreement with the observed stabilities due to different measurement methods. 

Similar anionic species HsMFe(CO)7 (M = Si, Ge) have resulted from exchange reactions (cf. Section III,B,9), while the rather weak unsym-metrical interaction of bases with (Cl3Si)2Fe(CO)4 gives rise to a related anion (Table XIII, entry 18). 

The variations observed in the thermodynamics of complexation of calix[4]pyrrole and its derivatives with the fluoride anion (Table 2) as a result of the medium effect are controlled by the solvation changes that reactants and product undergo in moving from one solvent to another. These differences in solvation are reflected in the thermodynamic parameters of transfer, AtP° for the reactants (fluoride and receptor) and the product (the anion complex) from a reference solvent, s-i to another solvent, s2. The relationship between these parameters and the thermodynamics of complexation, ACP°, in these solvents is shown in Equation (9). 

Sulfur forms many oxoacids, though few of them can be isolated in pure form. Most are prepared in aqueous solution or as crystalline salts of the corresponding oxoacid anions. Table 16.6.1 lists the common oxoacids of sulfur. 

Initiation with Tropylium Ion. When cycloheptatrienyl hexachlor-antimonate is used as initiator for tetrahydrofuran polymerization, the reactions are somewhat cleaner, and strong colors do not develop as readily as when the corresponding trityl salts are used (17). Rates of initiation are much lower, and the reaction is hardly noticeable at room temperature. However, at 50 °C. and above initiation is significant, and the polymerizations proceed almost to the expected theoretical conversion of monomer to polymer even when hexachlorantimonate is the anion (Table III). Therefore, the apparent low equilibrium conversion obtained with the rapidly initiating trityl salts is minimized in this case by the comparatively low rate of consumption of initiator. Once again GLC demonstrates clearly that the initiation reaction involves primarily hydride abstraction from the ether. 

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