Cation salt formation

Dissolve ca. 0 2 g. of product (I) in cold ethanol, and add with shaking 1-2 drops of dilute sulphuric acid. A deep purple coloration appears at once. This shows that salt formation has occurred on the quinoline nitrogen atom to form the cation (Ha), which will form a resonance hybrid with the quinonoid form tils). [Note that the forms (IIa) and (11b) differ only in electron position, and they are not therefore tautomeric.] If, hoAvever, salt formation had occurred on the dimethylaniino group to give the cation (III), thrs charge separiition could not occur, and the deep colour would be absent. 

Von Baeyer (Nobel Prize, 1905) should be credited for having recognized in 1902 the saltlike character of the compounds formed. He then suggested a correlation between the appearance of color and salt formation—the so-called halochromy. Gomberg (who had just shortly before discovered the related stable triphenylmethyl radical), as well as Walden, contributed to the evolving understanding of the structure of related cationic dyes such as malachite green. 

Salt formation with Brmnsted and Lewis acids and exhaustive alkylation to form quaternary ammonium cations are part of the rich derivati2ation chemistry of these amines. Carbamates and thiocarbamates are formed with CO2 and CS2, respectively the former precipitate from neat amine as carbamate salts but are highly water soluble. 

Salt Formation. As a weaMy basic pyrimidine and a thiazolium cation, thiamine forms both mono- and dipositive salts, eg, the two commercial... 

Salt Formation. Citric acid forms mono-, di-, and tribasic salts with many cations such as alkahes, ammonia, and amines. Salts may be prepared by direct neutralization of a solution of citric acid in water using the appropriate base, or by double decomposition using a citrate salt and a soluble metal salt. 

In a 1-substituted 1,2,3-triazole (79), both the 2- and 3-nitrogen atoms possess lone pairs of electrons that are available for quaternary salt formation, and quatemization is known to occur at the 3-nitrogen atom to give the symmetrical cation (80). Thus, the reaction between 1-methyl-l,2,3-triazole and benzyl iodide yields the same salt as is obtained from the interaction of 1-benzyl-1,2,3-triazole and methyl iodide the salt must therefore be 80 (R = Me, R = PhCH2,... 

As for the salt formation and single-electron transfer, thermodynamics for simple redox processes may be applied to predict their selectivity. As a first approximation, a cation with red lower and higher than 0.2 V would give a salt and a radical pair, respectively, when combined with [2 ]. In practice, the cations which were found to give salts with [2 ] have red values more negative than —0.8 V. On the other hand, quantitative single-electron transfer has been observed from [2 ] to the heptaphenyltropylium ion which is relatively unstable p/fR+ —0.54 in methanol (Battiste and Barton, 1968) and E ed —0.30 V vs. Ag/Ag in acetonitrile (Kitagawa et al., 1992). 

As the cation becomes progressively more reluctant to be reduced than [53 ], covalent bond formation is observed instead of electron transfer. Further stabilization of the cation causes formation of an ionic bond, i.e. salt formation. Thus, the course of the reaction is controlled by the electron affinity of the carbocation. However, the change from single-electron transfer to salt formation is not straightforward. As has been discussed in previous sections, steric effects are another important factor in controlling the formation of hydrocarbon salts. The significant difference in the reduction potential at which a covalent bond is switched to an ionic one -around -0.8 V for tropylium ion series and —1.6 V in the case of l-aryl-2,3-dicyclopropylcyclopropenylium ion series - may be attributed to steric factors. 

This concept covers most situations in the theory of AB cements. Cements based on aqueous solutions of phosphoric acid and poly(acrylic acid), and non-aqueous cements based on eugenol, alike fall within this definition. However, the theory does not, unfortunately, recognize salt formation as a criterion of an acid-base reaction, and the matrices of AB cements are conveniently described as salts. It is also uncertain whether it covers the metal oxide/metal halide or sulphate cements. Bare cations are not recognized as acids in the Bronsted-Lowry theory, but hydrated... 

As a cationic polymer and a cationic amphiphile, poly(allyl amine hydrochloride) (PAA) and octadecylamine (ODA) shown in Fig. 6 were used, respectively. The stability of the monolayers of the anionic amphiphiles was increased by polyion-complexation with PAA added in the aqueous subphase in comparison with Ca2+ salt formation. Ion complexation (1 1) of each anionic amphiphile with ODA was also performed at the air-water interface by spreading a chloroform solution of a 1 1 surfactant mixture. 

Chapter 18 by C. Chiappe focuses on the mechanism of bromination of alkenes, exploring the role of solvent on the formation of cyclic bromonium ion versus P-bromocarbemium ion, as key intermediates. In Chapter 19, H. P. A. Mercier et al. discuss the utility of a novel class of noble-gas onium salts as oxidants for generation and isolation of various trihalomethyl cation salts. 

The following cations have been used for salt formation sodium, calcium, barium, and manganese, as well as blends of calcium and manganese. European manufacturers continue to supply the calcium and manganese lakes, while the Japanese market also provides a barium lake. The latter, however, is of limited regional importance. 

Liu and Fedkiw proposed another SPE electrode formation method, in which cationic salt of platinum instead of chloroplatinic acid, which is used by Takenaka and Torikai, was first impregnated in Nafion and was later reduced chemically. a They showed that product distribution varies depending on the way of the deposition and oxidation conditions. ... 

In the dihydrochloride (602), the second molecule of acid is not firmly bound because of protonation of the second basic site by internal hydrogen bond formation. This would suggest that in the dipicrate, one mole of picric acid participates in salt formation, and that the second mole of picric acid is added to the hydrogen-bonded cation (LXI) forming a molecular complex. The existence of a monopicrate might thus serve to point out structures with steric inhibition of hydrogen bonding. 

Unlike thermal [2 + 2] cycloadditions which normally do not proceed readily unless certain structural features are present (see Section 1.3.1.1.), metal-catalyzed [2 + 2] cycloadditions should be allowed according to orbital symmetry conservation rules. There is now evidence that most metal-catalyzed [2 + 2] cycloadditions proceed stepwise via metallacycloalkanes as intermediates and both their formation and transformation are believed to occur by concerted processes. In many instances such reactions occur with high regioselectivity. Another mode for [2 + 2] cyclodimerization and cycloadditions involves radical cation intermediates (hole-catalyzed) obtained from oxidation of alkcnes by strong electron acceptors such as triarylammini-um radical cation salts.1 These reactions are similar to photochemical electron transfer (PET) initiated [2 + 2] cyclodimerization and cycloadditions in which an electron acceptor is used in the irradiation process.2 Because of the reversibility of these processes there is very little stereoselectivity observed in the cyclobutanes formed. 

ELECTRIDE. An experimental compound composed of an alkali-metal cation and an electron in which the electron functions as a chemical element te.g., a halogen) in salt formation. Several such compounds have been made in (he U.S. and abroad. The phenomenon is reported to be one that challenges accepted concepts of compound formation... 

Evidence supporting the formation of 1 1 addition compounds is further substantiated by the actual isolation of stable acyl cation salts (Chapter 3). Therefore, it is highly desirable to develop methods in which only a catalytic amount of Friedel-Crafts acid catalyst may be used for effective conversion. 

Quaternary ammonium salts of dantrolene and clodanolene have been prepared, and the effect of the organic cation on the aqueous solubility has been reported (Ellis et al., 1980). It was reasoned that since the hydantoin moiety in each drug is weakly acidic, a strong base should be found for salt formation. The 13 different quaternary ammonium compounds were therefore used in the hydroxide salt form. The acid-base reaction proceeded rapidly, and the salt products were stable during recrystallization steps. Of the four salts for clodanolene, the aqueous solubilities ranged from 2- to 100-fold that of clodanolene sodium, on a mass basis. Of the 11 salts for dantrolene, the benzyl-trimethyl ammonium salt exhibited comparable solubility to that of dantrolene sodium. Among the other 10 salts were several examples that yielded enhanced solubilities of up to 1000-fold that of the sodium salt. Twelve of the Lfteen salts successfully demonstrated muscle relaxant activity when administered orally. 

Fig. 9 Synthesis of guanidinium-based cationic steroids incorporating an acylhydrazone linker [115]. Due to the chemical nature of the final reagent, lipid incorporation and salt formation steps are inverted in this synthetic approach...

Thus far no reports have appeared on the isolation of 1,3-ditellurolylium cation salts in a pure state. Attempts to prepare 1,3-ditellurolylium boron tetrafluoride and its derivatives via treatment of 1,3-ditelluroles with tri-phenylmethyl boron tetrafluoride in MeCN solution failed (82TL1531). However, formation of the 1,3-ditellurolylium cation 74 was revealed by the H NMR spectrum in which the 2-H proton was shown to give a very low-field triplet (8 15.0 ppm, 4/Hh = 1.2 Hz). Cation 74 is sufficiently stable in solution only at low temperature. When an acetonitrile solution of 74 obtained from 1,3-ditellurole was heated to 30°C, the initial H NMR spectrum drastically changed to the A2X spectral pattern (8 13.8 ppm, d and 10.3 ppm, /, iJ = 6.9 Hz) corresponding to the spectrum expected for the 1,2-ditellurolylium cation 75. A plausible reaction scheme is shown below. A further elevation of the temperature of the solution resulted in an unidentified destruction process accompanied by the extrusion of elemental tellurium. 

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