Cations potassium

Newkome and co-workers have demonstrated the operation of a template effect in the formation of a pyrido-ester-crown. In the reaction shown in Eq. (2.8), they treated 2-clTloronicotinoyl cliloride with either the disodium or dipotassium salt of pentaethylene glycol. TJie two reactions were conducted under identical conditions except for the presence of sodium vs. potassium cations. Since the product is a six-oxygen macrocycle, its formation would be expected to be favored by K" rather than Na" counter ions for the glycolate. In fact, the yields of crown-lactone were 30% and 48% respectively when Na" and K" were the templating cations. 

Over the years, 18-crown-6 has probably been utilized in more applications than any other erown with the possible exception of dibenzo-18-crown-6. There are several reasons for this. First, simple syntheses of 18-crown-6 have been available for a long time and the molecule may be prepared from very inexpensive starting materials. Equally important, however, is the fact that 18-crown-6 is a very strong binder for a number of alkali metals, especially sodium and potassium cations. 

Compound 5 was analyzed by NMR spectroscopy to gain information relative to conformation and complexation preferences. When complexation with potassium cations was attempted, the N—CHj signals were affected more than others. When the cation present was Ag , the protons adjacent to sulfur were more strongly affected. This observation may indicate the relative binding sites for soft versus hard cations in this system. ... 

Tire reduction of TAF 100 by metallic potassium resulted in the formation at room temperature of the stable anion radical 109, which yielded a simple nine-line ESR pattern caused by the two sets of two equivalent nitrogens with Ani = 3.40 and An2 = 0.81 G (79JOC3211).Tlie nonequivalency of the nitrogens was explained by the association of the potassium cation with one of the two diazacylopentadienyl moieties (Scheme 44). 

If we were to conduct a second solubility experiment in which solutions of KI and NaN03 were mixed, we would find that no precipitate forms. This demonstrates that K and NO3 ions do not form a solid precipitate, so the bright yellow precipitate must be lead(II) iodide, Pbl2. As the two salt solutions mix, cations and r anions combine to produce lead(II) iodide, which precipitates from the solution. On standing, the yellow precipitate settles, leaving a colorless solution that contains potassium cations and nitrate anions. The molecular blowups in Figure depict these solutions at the molecular level. 

Table 8 5 shows that each of the four common s-block ions is abundant not only in seawater but also in body fluids, where these ions play essential biochemical roles. Sodium is the most abundant cation in fluids that are outside of cells, and proper functioning of body cells requires that sodium concentrations be maintained within a narrow range. One of the main functions of the kidneys is to control the excretion of sodium. Whereas sodium cations are abundant in the fluids outside of cells, potassium cations are the most abundant ions in the fluids inside cells. The difference in ion concentration across cell walls is responsible for the generation of nerve impulses that drive muscle contraction. If the difference in potassium ion concentration across cell walls deteriorates, muscular activity, including the regular muscle contractions of the heart, can be seriously disrupted. 

Hindered lithium dialkylamides can generate aryl-substituted carbenes from benzyl halides.162 Reaction of a,a-dichlorotoluene or a,a-dibromotoluene with potassium r-butoxide in the presence of 18-crown-6 generates the corresponding a-halophenylcarbene.163 The relative reactivity data for carbenes generated under these latter conditions suggest that they are free. The potassium cation would be expected to be strongly solvated by the crown ether and it is evidently not involved in the carbene-generating step. 

Due to the presence of low-temperature desorption peak a new desorption site was included to phenomenological model of TPD experiments previously used for the description of the Cu-Na-FER samples [5], The fit of experimental TPD curves was performed in order to obtain adsorption energies and populations for individual site types sites denoted A (A1 pair), B (sites in P channel (A1 at T1 or T2)), C (sites in the M channel and intersection (A1 at T3 or T4)) [3] and D (newly introduced site). The new four-site model was able to reproduce experimental TPD curves (Figure 1). The desorption energy of site D is cu. 82 kJ.mol"1. This value is rather close to desorption energy of 84 kJ.mol"1 found for the site B , however, the desorption entropy obtained for sites B and D are rather different -70 J.K. mol 1 and -130 J.K. mol"1 for sites B and D , respectively. We propose that the desorption site D can be attributed to so-called heterogeneous dual-cation site, where the CO molecule is bonded between monovalent copper ion and potassium cation. The sum of the calculated populations of sites B and D (Figure 2) fits well previously published population of B site for the Cu-Na-FER zeolite [3], Because the population of C type sites was... 

The solid-state structure of 72 (Figure 38) consists of a polymer of alternating THF-solvated potassium cations and diamidomethylzincate anions. The alternating zincate ions, which are rotated by about 180° with respect to each other, sandwich the potassium ions. Each potassium ion is -coordinated to one methyldiamidozincate and -coordinated to the other. The zinc-methyl and zinc-nitrogen bonds of the zincate ion are 1.954(5) and 1.989(8) A, respectively. 

In the literature the term soluble Prussian blue introduced by Keggin and Miles [5] to determine the KFeFe(CN)6 compound is still widely used. However, it is important to note, that the term soluble refers to the ease with which the potassium ion can be peptized rather than to the real solubility of Prussian blue. Indeed, it can be easily shown by means of cyclic voltammetry that the stability of Prussian blue films on electrode supports is nearly independent of their saturation by potassium cations. Moreover, Itaya and coworkers [9] have not found any appreciable amount of potassium ions in Prussian blue, which makes doubtful structures like KFeFe(CN)6. Thus, the above equation fully describes the Prussian blue/Prussian white redox reaction. 

R.J. Mortimer, P.J.S. Barbeira, A.F.B. Sene, and N.R. Stradiotto, Potentiometric determination of potassium cations using a nickel(II) hexacyanoferrate-modified electrode. Talanta 49, 271-275 (1999). 

A typical phase transfer catalytic reaction of the liquid/liquid type is the cyanation of an alkyl halide in an organic phase using sodium or potassium cyanide in an aqueous phase. When these phases are stirred and heated together very little reaction occurs. However, addition of a small amount of crown ether (or cryptand) results in the reaction occurring to yield the required nitrile. The crown serves to transport the cyanide ion, as its ion pair with the complexed potassium cation, into the organic phase allowing the reaction to proceed. 

Potassium cation affinities of several azoles and other compounds in the gas phase were calculated by hybrid density functional theory [B3-LYP with 6-311 + G(3df, 2p) basis set] <2003CEJ3383>. There is a striking difference in binding energies of 177- and 277-1,2,3-triazoles. Some of the collected data are as follows ... 

Several different types of species are illustrated in Figure 6.1. The potassium cation (K+) at the top of the figure is separated from the soil surface by water molecules and would thus be considered an outer-sphere species. The potassium cation near the bottom of the figure is directly connected to the soil particle by an ionic charge and is therefore an inner-sphere species. Above this is an inner-sphere phosphate directly bonded to a soil surface aluminum. Also shown are potassium cations attached (inner sphere) to colloidal clay (CC) and colloidal soil organic matter (COM). Each of these is a different species. 

Since opposite charges attract each other, the cations attract the anions, forming an ionic compound. Ionic compounds are neutral so that the number of positive charges would equal the number of negative charges. The potassium cation would attract the chloride anion to form the ionic compound potassium chloride, KC1. We call ionic compounds such as this salts. 

A further ion detected at m/z 362 was assigned as the dimer [2M + H + K]2+. Since it was the only doubly charged dimer observed, it seemed that the combination of two Ci2-CAPB molecules with one proton and one potassium cation yielded a particularly stable species. 

Figure 6.20 Action of a fluorescent PET potassium cation sensor as a molecular switch using a macrocyclic electron donor and anthracene fluorophore...

X-ray crystallographic analysis of the potassium complex of [5] confirmed, as expected, that these receptors form intramolecular 1 1 sandwich complexes with potassium cations (Fig. 8). 

Electrochemical complexation studies of [5], disappointingly, revealed that the reversible ferrocenoyl oxidation wave was not perturbed on addition of either sodium or potassium cations, implying that the complexed group 1... 

Proton nmr titration experiments of [26] and [27] with KPF6 in acetonitrile revealed that in solution both compounds form 1 1 intramolecular sandwich complexes with the potassium cation. A number of alkyl-, vinyl- and azo-linked bis(benzo-15-crown-5) ligands are well known to exhibit this mode of K+ coordination. In the case of [26], a solid-state potassium complex was isolated whose elemental analysis and fast-atom bombardment mass spectrum ([26] K+ = 1083 complex ion) was in agreement with 1 1 complex stoichiometry (Fig. 20). 

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