Interaction electrostatic, betaine

It is believed that this greater interaction of 812BMG with + anions than with cations is due, not to the zwitterionic betaine, B , but to the cationic protonated betaine, B8, in equilibrium with it. Although the concentration of B8 at p8 = 5.8 is very small, it is felt that strong electrostatic interaction between it and an anion can displace the zwitterion-cation equilibrium sufficiently to cause an appreciable effect. 

When normalized to unit surface area, the adsorption density of the anionic surfactant is higher on quartz than on Berea sandstone because quartz carries a more positive surface charge than the clays (The clays provide most of the surface area for adsorption in Berea sandstone). If it is assumed that the betaine adsorbs on sandstone at least in part by its cationic group, then the lower adsorption density of the betaine on quartz than on Berea sandstone can also be attributed to electrostatic interactions. Matrix grains of the size encountered in typical reservoir rocks have low specific surface areas. Accordingly, the absolute amount of surfactant adsorbed or the amount adsorbed per unit mass of rock is lower for a clean sand than for a sand containing clays (12, 34, 82). Therefore, the... 

In this report, we examine the effects of millimolar to molar levels of Cl" and of other anions on the electron transport activity of isolated PS2 particles. At a concentration approx, above 0.1 M) anions inactivate PS2 via chaotropic interactions that require neutralization of the negative particle charge by binding metal cations. Betaine is shown to protect the PS2 particles against anion-induced inactivation and removal of extrinsic proteins. Protection Is visualized to be due to a surface layer of betaine zwitterions, preferentially oriented with the positive end groups facing the particle surface. This dipole layer shields the PS2 particles against bulk phase anions both sterically and electrostatically-... 

A UV-visible spectroscopic study of 3 and related substances revealed a strong solvatochromic effect, which served as the basis of the establishment of a solvent polarity scale (Buncel and Rajagopal, 1989, 1990,1991). The theoretical study of Rauhut et al. (1993) was based on AMI methodology (Dewar and Storch, 1985,1989) but used a double electrostatic reaction field in a cavity, dependent on both the relative permittivity and the refractive index. Nuclear motions interact with the medium through the relative permittivity, but electronic motions are too fast only the extreme high-frequency part of the dielectric constant is relevant. These authors were able to evaluate solvent-specific dispersion contributions to the solvation energy. The calculations reproduced satisfactorily the experimental solvatochromic results for 3 in 29 different solvents. The method has also been successfully applied to other solvatochromic dyes, including Reichardt s .j,(30) betaine. 

Using steady-state absorption studies, several other authors examined the micropolarity of confined IL in microemulsions stabilized by ionic surfactants [64,85,87], For example, Sarkar and coworkers examined [bmim][BF ]/benzene mixtures stabilized by the anionic SAIL surfactant [bmim][AOT] and observed that, within the studied range, the A for solubilized MO continued to undergo redshift with increasing R [85, 87], In another work, Falcone and coworkers compared the micropolarities of [bmim][BF4]/benzene mixtures stabilized by cationic BHDC and nonionic TX-lOO surfactants using l-methyl-8-oxyquinolinium betaine (QB), a dye that locates mainly at the surfactant interfacial layer [64]. When [bmim][BF ] was added to both BHDC/benzene and TX-lOO/benzene systems, a larger hypsochromic shift was sensed by the probe in the former. This implies that the local environments in BHDC/benzene system are more polar. The authors ascribed this phenomenon to the strong electrostatic interactions between the [BFJ anion and the BHD moiety of the cationic surfactant. 

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