Solvent cationization

Cationization of starch by dry reaction with 2,3-epoxypropyltrimethylammonium chloride is a commercially significant process. The key to a dry reaction is an intimate, homogenous mixture of the reagent and the catalyst. One process38,39 describes an activator consisting of spray dried, precipitated silica with a surface area of 190m2/g (BET) that contains an alkaline agent such as calcium oxide or calcium hydroxide and/or silicates. Different ratios of silica to alkali and 1-3% catalyst (based 

Aluminosilicate clays (kaolinite) with a cation exchange capacity of 2.2meq/100g were blended with calcium oxide and starch prior to spray addition of the epoxide. The reaction proceeded at ambient temperature without mixing. Greater reaction efficiencies are claimed.43 

Salts and organic by-products, mostly the diol resulting from hydrolysis of the epoxide, from dry cationization are left in the starch. Trimethylamine, if formed, can be detected by its odor. It can be neutralized by subsequent addition of acid. Addition of a slightly soluble organic acid, such as fumaric or adipic acid, during the cationization both eliminates the odor and aids scale control in starch cooking equipment.44 

Cationization and carboxymethylation of starch in an extruder has been reported.45 17 Cationization of potato starch in a twin-screw extruder had an optimum reaction efficiency of 71%. Further work yielded 80% efficiency and products with 0.03-0.10 DS.44 Additional heat treatment of extruded products (made via reaction with quaternary ammonium reagents) with sodium trimetaphosphate or citric acid has improved reaction efficiencies and/or viscosities.48 Dry cationization in the presence of methanol and isopropanol49 or combined with microwave irradiation has also been done.50 

Cationization of waxy maize, corn and barley starches in aqueous alcohol slurries is most effective at 35-65% ethanol for all starch types a 1 1 starch to water ratio gave highest DS values.51 A process for making cationic or amphoteric starches in aqueous, alkaline alcoholic solvents has also been described.52 

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This theory is associated in its early protonic form with Franklin (1905, 1924). Later it was extended by Germaim (1925a,b) and then by Cady Elsey (1922,1928) to a more general form to include aprotic solvents. Cady Elsey describe an acid as a solute that, either by direct dissociation or by reaction with an ionizing solvent, increases the concentration of the solvent cation. In a similar fashion, a base increases the concentration of the solvent anion. Cady Elsey, in order to emphasize the importance of the solvent, modified the above defining equation to ... 

Thus, adds and bases do not react directly but as solvent cations and anions. Since emphasis is placed upon ionization interactions, inherent addity and basidty is neglected, as are interactions in the non-ionic state. The theory is a simple extension of the Arrhenius theory and suffers from... 

The composition of the electrolyte is quite important in controlling the electrolytic deposition of the pertinent metal, the chemical interaction of the deposit with the electrolyte, and the electrical conductivity of the electrolyte. In the case of molten salts, the solvent cations and the solvent anions influence the electrodeposition process through the formation of complexes. The stability of these complexes determines the extent of the reversibility of the overall electroreduction process and, hence, the type of the deposit formed. By selecting a suitable mixture of solvent cations to produce a chemically stable solution with strong solute cation-anion interactions, it is possible to optimize the stability of the complexes so as to obtain the best deposition kinetics. In the case of refractory and reactive metals, the presence of a reasonably stable complex is necessary in order to yield a coherent deposition rather than a dendritic type of deposition. 

In alicyclic hydrocarbon solvents with aromatic solutes, energy transfer (vide infra) is unimportant and probably all excited solute states are formed on neutralization of solute cations with solute anions, which are formed in the first place by charge migration and scavenging in competition with electron solvent-cation recombination. The yields of naphthalene singlet and triplet excited states at 10 mM concentration solution are comparable and increase in the order cyclopentane, cyclohexane, cyclooctane, and decalin as solvents. Further, the yields of these... 

It was Ayusman Sen [8] who discovered in 1982 that the use of weakly coordinating anions and phosphines as the ligands together with palladium yielded much more stable and active catalysts for the formation of polyketone from CO and ethene in alcoholic solvents. Cationic palladium-(triphenylphosphine)2(BF4)2 gave a mixture of oligomers having methoxy ester... 

At 25°C, the cyclohexane molecules mainly have the chair form. The equilibrium concentration of the isomeric twist form is —10 " mol dm On ionization, the solvent cation-radicals in the chair form are predominant. Electron transfer between the chair form of the cyclohexane cation-radicals and the chair-shaped surrounding cyclohexane (neutral) molecules is very fast, since it requires minimum reorganization energy. However, the chair-form cation-radical sometimes approaches a minor part of the neutral molecules in the twisted form. Because the twisted cyclohexane has lower IP, the twist-shaped molecules scavenge the cation-radicals in the chair form. 

Carbon disulfide is isovalent to carbon dioxide and it also has a bent monomer anion. While gas-phase CO2 has negative EAg of —0.6 eV [24], for CS2, EAg is +0.8 eV [34]. Despite this very different electron affinity, Gee and Freeman [34] observed long-lived electrons in CS2 (with lifetime > 500 psec) with mobility ca. 8 times greater than that of solvent cations. Over time, these electrons converted to secondary anions whose mobility was within 30% of the cation mobility. Between 163 and 500 K, the two ion mobilities scaled linearly with the solvent viscosity, as would be expected for regular ions. Of course, Gee and Freeman s identification of the long-lived high-mobility solvent anions as electron is just a manner of speech Obviously, quasifree or solvated electrons cannot survive for over a millisecond in a positive-EAg liquid. 

Hummel and Luthjens [398] formed electron—cation pairs in cyclohexane by pulse radiolysis. With biphenyl added to the solvent, biphenyl cations and anions were formed rapidly on radiolysis as deduced from the optical spectra of the solutions. The optical absorption of these species decreased approximately as t 1/2 during the 500 ns or so after an 11ns pulse of electrons. The much lower mobility of the molecular biphenyl anion (or cation) than the solvated electron, es, (solvent or cation) increases the timescale over which ion recombination occurs. Reaction of the solvated electron with biphenyl (present in a large excess over the ions) produces a biphenyl anion near to the site of the solvated electron localisation. The biphenyl anion can recombine with the solvent cation or a biphenyl cation. From the relative rates of ion-pair reactions (electron-cation, electron—biphenyl cation, cation—biphenyl anion etc.), Hummel and Luthjens deduced that the cation (or hole) in cyclohexane was more mobile than the solvated electron (cf. Sect. 2.2 [352, 353]). 

A solution of cations of a higher valence than that of the solvent cation must be accompanied by one or more anion vacancies. For example, consider the presence of Fe+3 ions in FeO. For every two Fe+3 ions, there is an O-2, vacancy, as shown in Figure 5.2C. 

The simulations in the dry and in the humid RTIL started with 12 crowns (Q form) "diluted" in the solvent box. The crowns rapidly underwent a conformational change to D3d, showing that this structure is more stable in the two forms of the RTIL. Typical snapshots at the end of the dynamics (1.5 ns) and radial distribution functions (see Figure 10) reveal the importance of solvent cations. 

In the humid RTIL, somewhat different solvation patterns are observed. Ten of the twelve crowns are solvated as in the dry liquid, with about one BMI+ cation at each face, while the two others are solvated by 1 BMf + 1 H20, or by 1+1 H20 molecules (Figure 10). Interestingly, the "first shell" H20 molecules sit in bridging position as described in section 1, and are further stabilized by second shell interactions with other H20, or BMI1 species. In the two forms of the liquid, there is no solvent anion at less than 7 A from the center of the crown, thus confirming the importance of the solvent cations and, to a lesser extent, of water. Comparison of the two forms of the RTIL shows that one 18C6 interacts somewhat more with the humid than with the dry liquid (-64 and -58 kcal/mol, respectively). 

Cyclopentanedione and 1,3-cyclohexanedione are highly enolized ketones. Will they give the same proportions of O- and C-alkylations under the same reaction conditions (of solvent, cation, etc.) ... 

Instead of the conventional gel-like structures, that swell in contact with a solvent, cation exchangers may be synthesized as a macroreticular polymer. 

The reaction of the primary solvent cations (or holes) with monomers to yield styrene radical cation is very fast (k 10u mol 1dm3s-1). The produced... 

Similar to the behavior of nonactive metal electrodes described above, when carbon electrodes are polarized to low potentials in nonaqueous systems, all solution components may be reduced (including solvent, cation, anion, and atmospheric contaminants). When the cations are tetraalkyl ammonium ions, these reduction processes may form products of considerable stability that dissolve in the solution. In the case of alkali cations, solution reduction processes may produce insoluble salts that precipitate on the carbon and form surface films. Surface film formation on both carbons and nonactive metal electrodes in nonaqueous solutions containing metal salts other than lithium has not been investigated yet. However, for the case of lithium salts in nonaqueous solvents, the surface chemistry developed on carbonaceous electrodes was rigorously investigated because of the implications for their use as anodes in lithium ion batteries. We speculate that similar surface chemistry may be developed on carbons (as well as on nonactive metals) in nonaqueous systems at low potentials in the presence of Na+, K+, or Mg2+, as in the case of Li salt solutions. The surface chemistry developed on graphite electrodes was extensively studied in the following systems ... 

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