Cation hydration

Calculated using Eqs. (45), (49), (46), (50), and (51) for hydrated cations, nonhydrated cations, hydrated anions, nonhydrated anions, and polyanions, respectively. 

In dehydrated CoAF the migration of Co2+ ions from Co2 to Co2a sites on heating (Fig. lb) allows the occupancy of the most active a-sites where Co2+coordinates four framework oxygens. The irreversible and progressive decline of catalytic activity during dry-wet-dry cycles is likely to be due to cation hydration and movement from those sites, thus, decreasing their occupancies. 

Toteja RSD, Jangida BL, Sundaresan M, Venkataramani B (1997) Water sorption isotherms and cation hydration in dowex 50w and amberlyst-15 ion exchange resins. Langmuir 13 2980-2982... 

Acyl complexes can also result from the reaction of terminal alkynes with cationic, hydrated complexes of iron (Entry 4, Table 2.7) [47]. An electrophilic vinylidene complex is probably formed as intermediate this then reacts with water and tautomerizes to the acyl complex. 

Both type I and type II water forms were detected, and the I/II mole ratio was rather constant at 1 2.2 for the Na+ form having the low H2O/SO3 mole ratios of 0.06, 0.5, and 1.2. These numbers were derived from the areas under the two deconvoluted peaks. The ratio of type I to II water molecules decreases in the order for the series Na+ > K+ > Rb+ > Cs+, which is reasonable considering that the cation hydration number decreases in this order and shows the structure-breaking action of cations with... 

Using a simple electrostatic interaction-based model factored into reaction rate theory, the energy barrier for ion hopping was related to the cation hydration radius. The conductance versus water content behavior was suggested to involve (1) a change in the rate constant for the elementary ion transfer event and (2) a change in the membrane microstructure that affects conduction pathways. 

A more complete and much more rigorous description of bonding in complexes would be provided by a quantum mechanical treatment. Such a treatment is especially needed in the case of departures from the ionic model and increasing contribution of covalent bonding (ion pairs, soft donors and acceptors). However only a few studies have been reported. They are mainly concerned with cation hydration and use either semi-empirical 19—21) or non-empirical methods 22—24). A non-empirical treatment of cation NH3 systems has also been performed recently (25). However the present state of the computations is still far from providing a complete description of the system including the medium. The latter may be taken into account by a Bom-type "solvaton (27,26). Heats of hydration may then be calculated (27). A discussion of this aspect of the problem is deferred to a later date, awaiting especially a more complete analysis of non-empirical calculations. In the course of the discussion of... 

Diuretics, interaction with lithium, 36 65-66 Divalent cations hydration shell, 34 211 structure, 34 210-212... 

Monophosphabutadienes, 33 281-283 Monophosphacarbodiimides, 33 322 preparation, 33 323 reactivity, 33 322-325 stereoselective reaction, 33 324 Monophosphahexadienes, 33 305, 307-310 Monoterpyridine complexes of copper, 45 288 Monovalent cations hydration shell properties, 34 203-204 structure, 34 202-205... 

The AS-values increased with respect to those of the dehydrated samples (8), especially for the samples with high H20/cation ratios. This means that there is a distortion of the cationic hydration shell or a partial dehydration of the cations during migration (18). In other words, water around the migrating cations cannot be regarded water of hydration. In that respect, hydrated zeolites resemble concentrated cationic solutions (19). 

Group VI. O-Donor ligands. 1H N.m.r. shifts have been measured for aqueous AgN03 and AgBF4 between 15 and 100°C.200 The very small influence of the salts on the chemical shift of H20 is attributed to almost exact cancellation of upheld anionic and downfield cationic contributions. The cationic hydration number appears to be less than 1 owing to the lability of the complex. 

Examination of the structures of Ln(III) hydrates in crystals and our knowledge of Ln(III) complexes in solution now throws up a problem which the above equations do not readily meet. There is no certain distinction between inner and outer sphere for ions such as Ln(III). Firstly the inner sphere is constantly switching between 8- and 9-coordination but 9-coordination is not far from 6-innermost water molecules which can distort to an octahedron and 3-outermost water molecules. The steps of kinetics can involve multiple re-arrangements of the cation hydration shell which is itself variable in the series of Ln(III). The model equations above are only guides to thinking. 

The latter equation shows that the cation hydration (described by the cut-off distance d2) dominates the process. Because of the increase in potential with electrolyte concentration, the region between dx and d2 is practically depleted of anions. 

Can the change in cation hydration, between bulk and interface explain this effect If the cations (such as Na+ or K+) cannot approach the interface, and the potential well for anions is not very deep, the overall adsorption of ions is negative at any electrolyte concentration. However, if the cations (such as H+) can penetrate at least a part of the interfacial potential well of the anions (d2[Pg.414]

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