Ions, specific interactions between

Bostrom, M., F. W. Tavares, D. Bratko, and B. W. Ninham. 2006. Ion specific interactions between pairs of nanometer sized particles in aqueous solutions. Progress in Colloid and Polymer Science 133 74—77. 

In porous separators the pore radii are large compared to the size of molecules. Hence, interaction between the electrolyte and the pore walls has practically no qualitative effects on the ionic current through the separator the transport numbers of the individuaf ions have the same vafues in the pores as in the bulk electrolyte, hi swollen membranes the specific interaction between individuaf ions and macromofecufes is very pronounced. Hence, these membranes often exhibit sefectivity in the sense that different ions are affected differentfy in their migration. As a resuft, the transport numbers of the ions in the membrane differ from those in the efectrofyte outside the membrane. In the limiting case, certain types of ion are arrested completely, and the membrane is called permselective (see Chapter 5). 

The approach introduced by E. A. Guggenheim and employed by H. S. Harned, G. Akerlof, and other authors, especially for a mixture of two electrolytes, is based on the Br0nsted assumption of specific ion interactions in a dilute solution of two electrolytes with constant overall concentration, the interaction between ions with charges of the same sign is non-specific for the type of ion, while interaction between ions with opposite charges is specific. 

Guggenheim used this assumption to employ Eq. (1.3.38) for the activity coefficient of the electrolyte, where the product aB was set equal to unity and the specific interaction between oppositely charged ions was accounted for in the term CL Consider a mixture of two uni-univalent electrolytes AlBl and AUBU with overall molality m and individual representations yl = milm and yn = mulm, where mx and mn are molalities of individual electrolytes. According to Guggenheim,... 

Lipophilic ion exchangers traditionally used for polymeric membrane preparation are the anionic tetraphenylborate derivatives and the cationic tetraalkylammonium salts. The charges on both lipophilic ions are localized on a single (boron or nitrogen) atom, but the steric inaccessibility of the charged center, due to bulky substituents, may inhibit ion-pair formation in the membrane and provide, when necessary, non-specific interactions between ionic sites and sample ions. 

It was found that a better representation of non-specific interactions between solvents and the monosubstituted dipolar trimethylammonium ions is gained from the product of tt and the solvent dipole moment (/x). The obtained results were compared with the gas-phase basicity and the solvent attenuation factors (SAF) were calculated". 

A simple extension of the retention model discussed so far is to include the possibility for a specific interaction between the analyte and the pairing ion. By using a similar reasoning as for the electrochemical potential shown above, it is easily shown that the retention factor follows the relation... 

Agresti, C., Tu, Z., Ng, C., Yang, Y., and Liang, J. F. (2008). Specific interactions between diphenhydramine and a-helical poly(glutamic acid)—A new ion-pairing complex for taste masking and pH-controlled diphenhydramine release. Eur. J. Pharm. Biopharm. 70 (1), 226-233. 

More recently an oil continuous microemulsion technique has been described,16 which allows the study of specific interactions between amino acid side chains and metal ions. Both the metal ion and amino acid are microencapsulated as aqueous droplets in a dispersed phase. The technique is of particular relevance to metalloprotein and metal-membrane interactions where the local dielectric constant can be considerably less than that of bulk water. 

Electronic properties of intrazeolitic complexes of transition metal ions with oxygen are of Interest for elucidation of oxygen binding and its activation for oxidation reactions. In an earlier study, dioxygen and monooxygen chromium species were reported to be formed by specific interactions between the oxygen molecules and the Cr ions planted in the Type A zeolite (1). 

Because of the possibility of charge-transfer interactions between polar head and halide ion, ion specific interactions can be expected to be particularly marked for alkylpyridinium halides. From the CMCs counterion dependence3, as well as from counterion dissociation studies, binding is found to follow the sequence I- > Br > CP. The size of hexadecylpyridinium micelles is very sensitive to the anion of added salt, aggregation being promoted according to the sequence227 F [Pg.52]

In order to develop selective electrodes, it is necessary to introduce specific interactions between the ionophore and the anion of interest. This can be achieved by designing an ion carrier whose structure is complementary to the anion. This type of design can be based on molecular recognition principles, such as the ones that involve complementarity of shape and charge distribution between the ion and the ionophore. 

N,N-Diethyl-4-nitroaniline, has an aromatic ring but no hydrogen bond donor substituent, shows a n-jt transition based on a non-specific interaction between ions. Dipolarity/polarizability, jz, is estimated by the solvatochromic shift of N,N-diethyl-4-nitroaniline using Eq. (3.3), where Amax is the absorption maximum for N, N-diethyl-4-nitroaniline. 

A simple model that accounts for the large specific interactions between ions and surfaces is based on the long-known role of ions in structuring the water around them the structure-making ions interact preferentially with the bulk water, hence they are effectively repelled by the surface, while the structure-breaking ions disturb the... 

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