Counterions tetraethylammonium

In this work, the counterion tetraethylammonium (TEA) is chosen as a reference... 

As expected, HTMAB made a respectable showing in these experiments. Trioctylmethylammonium chloride (TOMAC) and trioctylmetliylammonium bromide (TOMAB) outperformed all other catalysts. It was postulated that the three octyl groups were the proper length for solvation of the polymer while at the same time small enough to avoid sterically hindering the reaction. In order to determine if TOMAB could be used to catalyze PET depolymerization for more than one treatment cycle, the catalyst was recovered upon completion of one treatment and added to a second run for 60 min. Tetraethylammonium hydroxide (TEAOH) was studied as a catalyst in order to demonstrate the effect of hydroxide ion as a counterion. The percent PET conversion for the second cycle was 85.7% compared to a conversion of 90.4% for the first treatment cycle. 

When a tetraalkylammonium cation is used as a counterion in solvents of high polarity, such as AN or DME, the alkyl groups of the cation hinder the mutual approach of species with different charges. Ion pairs with the potassium cation are stable. This follows from a comparison of the polarographic behavior of the three isomeric dinitrobenzenes in the same solvent (DMF) using tetraethylammonium or potassium perchlorate as the carrier electrolyte (Todres 1970). The halfwave potentials corresponding to the conversion of p- and m-dinitrobenzenes into anion-radicals are independent of whether tetraethylammonium or potassium counterions are employed. The anion-radical is formed from o-dinitrobenzene at a potential that is less negative by almost 100 mV when... 

The complexes undergo weak antiferromagnetic interactions with exchange proceeding via the halide bridges. The counterion may have a marked effect on the structure for [Cr2Cl9]3-, change of the counterion from potassium to tetraethylammonium is accompanied by a decrease... 

Benrraou M, Bales BL, Zana R (2003) Effect of the nature of the counterion on the properties of anionic surfactants. 1. cmc, ionization degree at the cmc and aggregation number of micelles of sodium, cesium, tetramethylammonium, tetraethylammonium, tetrapropylammonium, and tetrabutylammonium dodecyl sulfates. J Phys Chem B 107 13432-13440... 

Benrraou et al. (2003) studied the interaction between nonionic polymers and anionic surfactants. The polymers used were poly(ethylene oxide) and poly(vinylpyrrolidone) and the surfactants used were cesium and tetraalkylammonium (tetramethyl to tetrabutyl ammonium) dodecylsulfates. They used the electrical conductivity method to determine the CAC for different polymer-surfactant combinations. They concluded that the value of the ratio CAC/CMC increases with the increase in the radius of the counterion. Thus, the strength of interaction decreases upon increasing the counterion radius. The sequence in which the ratio CAC/CMC varied is as follows Na < Cs+ < tetramethylammonium+ < tetraethylammonium+ = tetrapropylammonium+ = tetrabutylam-monium+ = 1.0. The ratio CAC/CMC is unity in the case of the last three large-size ions indicating the absence of any interaction. For small ions such as Na+, the CAC/CMC ratio is less than unity indicating significant interaction. 

The rate at which a surfactant reaches equilibrium surface tension also depends on its counterion. Klein et al. found that the tetraethylammonium salt of per-fluorooctanesulfonic acid attains surface tension equilibrium more rapidly than the potassium salt (Fig. 4.27) [49], the tetramethylammonium, or the ammonium salt (Table 4.6) [61]. 

The solubilities of the salts of pejfluoroalkanesulfonic acids depend on the nature of the counterion. The sodium and potassium salts of Ci, C2, and C3 per-fluoroalkanesulfonic acids are soluble in water, but their solubilities decrease with increasing chain length [6]. The tetraethylammonium salt of perfluorooctanesul-fonic acid is more soluble in water than the potassium salt and is soluble in organic solvents such as alcohols, dimethyl formamide (DMF), or dimethyl sulfoxide (DMSO) as well [7]. 

Bossev et al. [141,142] studied the counterion effect on micellar systems formed by tetraethylammonium perfluorooctylsulfonate (TEAFOS) and lithium perfluorooctylsulfonate (LiFOS). H- and -NMR measurements of self-diffu-sion coefficients and chemical shifts showed that LiFOS, which forms spherical micelles, has a fast exchange rate. The TEA counterions induce a transformation to threadlike structures. As a result, the self-diffusion coefficient for TEAFOS is by a magnitude lower than that of LiFOS. 

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