Salt effect, anion

The distribution of highly extractable solutes such as and Pu between the aqueous and organic phases is strongly dependent upon the nitrate anion concentration in the aqueous phase. This salting effect permits extraction or reextraction (stripping) of the solute by controlling the nitric acid concentration in the aqueous phase. The distribution coefficient, D, of the solute is expressed as... 

The concentration of salt in physiological systems is on the order of 150 mM, which corresponds to approximately 350 water molecules for each cation-anion pair. Eor this reason, investigations of salt effects in biological systems using detailed atomic models and molecular dynamic simulations become rapidly prohibitive, and mean-field treatments based on continuum electrostatics are advantageous. Such approximations, which were pioneered by Debye and Huckel [11], are valid at moderately low ionic concentration when core-core interactions between the mobile ions can be neglected. Briefly, the spatial density throughout the solvent is assumed to depend only on the local electrostatic poten-... 

Winstein suggested that two intermediates preceding the dissociated caibocation were required to reconcile data on kinetics, salt effects, and stereochemistry of solvolysis reactions. The process of ionization initially generates a caibocation and counterion in proximity to each other. This species is called an intimate ion pair (or contact ion pair). This species can proceed to a solvent-separated ion pair, in which one or more solvent molecules have inserted between the caibocation and the leaving group but in which the ions have not diffused apart. The free caibocation is formed by diffusion away from the anion, which is called dissociation. 

Salt effects on the reaction of 2,4-dinitrochlorobenzene with amines or alkoxides have been investigated.Reinheimer et al. have studied decelerative ion pairing of alkali metal methoxides in reaction with this substrate cations and anions in added salts have specific effects on ion pairing. 

Above pH 5 the reaction presumably involves two anions and, indeed, a positive salt effect is found and the rate expression is... 

The decomposition of the salt [(cp)Fe(CgHg) Na+] displaces the equilibrium with the participation of this salt to the right. Hence, the difference in stability of the (20e) anion (cp)Fe(CgHg) depending on the cation nature is the major factor responsible for the salt effect. The NaPFg salt can induce electron transfer between neutral organometallic species very efficiently. 

Zinc dialkyl/diaryl dithiophosphates are widely used as antiwear additives in engine oils to protect heavily loaded engine parts from excessive wear. They are also used as antiwear agents in hydraulic fluids. The salts are effective oxidation and corrosion inhibitors, they also act as detergents. During friction, these salts form anion-radicals that are successfully cleaved (Kajdas et al. 1986). 

Adverse effects include abdominal pain, diarrhoea and nausea. Electrolyte disturbances, can result from absorption. From the various inorganic salts both anions and cations can be absorbed. Magnesium levels can be raised in patients with renal impairment. 

We have made no systematic studies of ionic strength effects. Ionic strength does not seem important in the catalytic hydrolysis of the acylnitrophenolates, which carry no charge. There are substantial salt effects in the decarboxylation reaction with nitrobenzisoxazole, which is an anionic substrate. These may reflect general ion cloud effects or anionic competition for binding to the polymer. 

We can now discuss the solvation number. In systems such as the metha-nol-water-CaCl2 system shown in Figure 5, the hydration number is the greatest, that is, 11 at x3 = 0.020. If the hydration number of ions is calculated from the hydration entropy, Ca2+ is seven and Cl is two (3). If it is assumed that CaC is completely dissociated and both the cation and anion forms hydrate, the hydration number becomes 7 + 2X2 = 11, which agrees with the value obtained from the salt effect. 

As previously stated, Gross (51) and Larsson (52) suggested that the salt effect is an additive function of two constants characteristic of the cation kc, and the anion, k i.e., log So/S = kscs = (k + kc)cs- In these studies Larsson assumed K+ = kc - Individual ion contributions have also been devised in volume studies with the additivity often extending to moderate concentrations (53) and enthalpy studies (54). 

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