Complexation Of Sodium Cation Research Articles

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Minerals dissolved in water have an important effect on the overall chemistry of the brewing process. Ions from these minerals affect the pH of water, its hardness, alkalinity and mineral composition. These parameters are the most important factors in determining the suitability of water for brewing, in particular for the mashing process. For that reason, it is very important to study the ion-salt composition of mash water and its influence on the quality of beer. The method of regulating the ion-salt composition of water, which is necessary for its use in the mashing process in order to obtain high-quality beer is discussed in the article. Prepared water obtained by reverse osmosis is free from ions as much as possible, which enabled to prepare water with the necessary ion-salt composition for rubbing by adding appropriate salts. Using prepared water in the mashing process, beer samples were obtained, which were evaluated according to sensory and physicochemical indicators. The effect of ion-salt composition of mash water on beer quality indicators was studied. It was found that calcium and sodium cation complexes, as well as a mixture of sulfates and chlorides dissolved in the water used for the mashing process, have the most significant impact on beer quality. Concentrations of individual ions in such water do not show any pronounced dependence on beer quality indicators. It was studied that the increase in the ratio of cations Ca2+/Na+ and sulfates and chlorides SO4 2- /Cl in the mash water has a positive effect on the sensory and quality indicators of beer: the ratio of key ions affects hop bitterness to the greatest extent among the quality indicators of beer. In addition, the ratio of Ca2+/Na+ cations has a positive effect on the foam resistance of beer, and the ratio of sulfates and chlorides SO4 2- /Cl leads to an increase in the share of alcohol in the finished drink. According to the tasting evaluation of beer, samples with a higher ratio of key ions have a brighter taste and aroma.

A Photoprotective Effect by Cation-π-Interaction? Quenching of Singlet Oxygen by an Indole Cation-π Model System.

We investigated the effect of the cation-π interaction on the susceptibility of a tryptophan model system toward interaction with singlet oxygen, that is, type II photooxidation. The model system consists of two indole units linked to a lariat crown ether to measure the total rate of removal of singlet oxygen by the indole units in the presence of sodium cations (i.e. indole units subject to a cation-π interaction) and in the absence of this interaction. We found that the cation-π interaction significantly decreases the total rate of removal of singlet oxygen (kT ) for the model system, that is, (kT =2.4±0.2)×108 m-1 s-1 without sodium cation vs (kT =6.9±0.9)×107 m-1 s-1 upon complexation of sodium cation to the crown ether. Furthermore, we found that the indole moieties undergo type I photooxidation processes with triplet excited methylene blue; this effect is also inhibited by the cation-π interaction. The chemical rate of reaction of the indole groups with singlet oxygen is also slower upon complexation of sodium cation in our model system, although we were unable to obtain an exact ratio due to differences of the chemical reaction rates of the two indole moieties.

Chalcogen Bond Mediated Enhancement of Cooperative Ion‐Pair Recognition

AbstractA series of heteroditopic receptors containing halogen bond (XB) and unprecedented chalcogen bond (ChB) donors integrated into a 3,5‐bis‐triazole pyridine structure covalently linked to benzo‐15‐crown‐5 ether motifs exhibit remarkable cooperative recognition of halide anions. Multi‐nuclear 1H, 13C, 125Te and 19F NMR, ion pair binding investigations reveal sodium cation–benzo‐crown ether binding dramatically enhances the recognition of bromide and iodide halide anions, with the chalcogen bonding heteroditopic receptor notably displaying the largest enhancement of halide binding strength of over two hundred‐fold, in comparison to the halogen bonding and hydrogen bonding heteroditopic receptor analogues. DFT calculations suggest crown ether sodium cation complexation induces a polarisation of the sigma hole of ChB and XB heteroditopic receptor donors as a significant contribution to the origin of the unique cooperativity exhibited by these systems.

Chalcogen Bond Mediated Enhancement of Cooperative Ion-Pair Recognition.

A series of heteroditopic receptors containing halogen bond (XB) and unprecedented chalcogen bond (ChB) donors integrated into a 3,5‐bis‐triazole pyridine structure covalently linked to benzo‐15‐crown‐5 ether motifs exhibit remarkable cooperative recognition of halide anions. Multi‐nuclear 1H, 13C, 125Te and 19F NMR, ion pair binding investigations reveal sodium cation–benzo‐crown ether binding dramatically enhances the recognition of bromide and iodide halide anions, with the chalcogen bonding heteroditopic receptor notably displaying the largest enhancement of halide binding strength of over two hundred‐fold, in comparison to the halogen bonding and hydrogen bonding heteroditopic receptor analogues. DFT calculations suggest crown ether sodium cation complexation induces a polarisation of the sigma hole of ChB and XB heteroditopic receptor donors as a significant contribution to the origin of the unique cooperativity exhibited by these systems.

Peculiarities of complexation of sodium cations by star-shaped polymers with core formed from diepoxides and poly(ethylene oxide) arms

23Na NMR spectroscopy was used to study complexation of sodium cations (NaClO4) with a few of star-shaped polyethers. The bonding of sodium ions by these polymers having PEO arms and with model compounds has been studied in anhydrous methanol solutions. In this paper the preliminary studies are presented, indicating that star polymers built from PEO arms and core formed from diepoxides, containing cyclic structures, are good polydentate complexing agents of sodium cations. Core cyclic structures hinder exchange of the complexed sodium cation with free cations.

Experimental and Theoretical Studies of Sodium Cation Complexes of the Deamidation and Dehydration Products of Asparagine, Glutamine, Aspartic Acid, and Glutamic Acid

The deamidation and dehydration products of Na+(L), where L = asparagine (Asn), glutamine (Gln), aspartic acid (Asp), and glutamic acid (Glu), are examined in detail utilizing collision-induced dissociation (CID) with Xe in a guided ion beam tandem mass spectrometer (GIBMS). Results establish that the Na+(L) complexes decompose upon formation in our dc discharge/flow tube ion source to form a bis-ligand complex, Na+(L-HX)(HX), composed of a sodium cation, the (L-HX) decomposition product, and HX, where HX = NH3 for the amides and H2O for the acids. Analysis of the energy-dependent CID cross sections for the Na+(L-HX)(HX) complexes provides unambiguous identification of the (L-HX) fragmentation products as 3-amino succinic anhydride (a-SA) for Asx and oxo-proline (O-Pro) for Glx. Furthermore, these experiments establish the 0 K sodium cation affinities for these five-membered ring decomposition products and the H2O and NH3 binding affinities of the Na+(a-SA) and Na+(O-Pro) complexes after accounting for unimolecular decay rates, the internal energy of reactant ions, and multiple ion-molecule collisions. Quantum chemical calculations are determined for a number of geometric conformations of all reaction species as well as a number of candidate species for (L-HX) at the B3LYP/6-311+G(d,p) level with single-point energies calculated at MP2(full), B3LYP, and B3P86 levels using a 6-311+G(2d,2p) basis set. This coordinated examination of both the experimental work and quantum chemical calculations allows for a complete characterization of the products of deamidation and dehydration of Asx and Glx, as well as the details of Na+, H2O, and NH3 binding to the decomposition species.

Quantum chemical analysis of possible fragmentation of [M + H]+ and [M + Na]+ complexes of monosubstituted methane, cyclohexane, and benzene derivatives in mass spectrometric studies

The formation and fragmentation energies of the proton and sodium cation complexes with monosubstituted methane, cyclohexane, and benzene derivatives in which carbon atoms are bonded to substituents (NH2, OH, F, Cl, Br, ONO2, NO2, COOH, CN, and Ph) were calculated by the B3LYP/6-31G(d) method. For [M + Na]+ complexes, the formation energies are much lower (and differ from one another to a much lesser extent), while the dissociation energies are much higher, than the corresponding energies of the [M + H]+ complexes. Na+ cation shows a lower selectivity toward localization at functional groups in molecules compared to H+.

Modeling Acid and Cationic Catalysis on the Reactivity of Duocarmycins

Several catalyzed alkylation reactions of 9-methyladenine by a model [CPI, cyclopropa[c]pyrrolo[3,2-e]indol-4(5H)-one (1)] of duocarmycin anticancer drugs have been compared to the uncatalyzed reaction in gas phase and in water solvent bulk, using density functional theory at the B3LYP level with the 6-31+G(d,p) basis set and C-PCM solvation model. The effect on the CPI reactivity induced by water, formic and phosphoric acids (general acid catalysis), H3O+ (specific acid catalysis), sodium, and ammonium cation complexation (cationic catalysis) has been investigated. The calculations indicate that the specific acid catalysis and the catalysis induced by sodium cation complexation are strong in the gas phase, but solvation reduces them dramatically by electrostatic effects. The specific acid catalysis is still operative, but strongly reduced in water solution, where the reaction barrier is reduced by 8.6 kcal mol(-1) in comparison to the uncatalyzed reaction. The general acid catalysis induced by phosphoric acid (-7.3 kcal mol(-1)) and the catalysis induced by Na+ and NH4+ complexation become competitive, with a catalytic effect of -3.6 and -4.1 kcal mol(-1) in water, respectively. With the specific acid catalysis, the high acidity (low pK(a) value) of the conjugated acid of CPI (CPIH+), computed in water solution using both C-PCM (pK(a) = +2.6) and PCM-B3LYP/6-31+G(d,p) (pK(a) = +2.4) solvation models, suggests that the catalytic effects induced by NH4+ complexation could become more important than the specific acid catalysis and the general catalysis by H3PO4 under physiological conditions, due to concentration effects of the catalysts.

The low energy tautomers and conformers of the dipeptides HisGly and GlyHis and of their sodium ion complexes in the gas phase

The low-lying conformers of the dipeptides HisGly and GlyHis, and of their sodium cation complexes, have been studied with a combination of Monte Carlo search with the Amber force field and local geometry optimization at the ab initio HF/6-31G(d) level, completed with MP2(full)/6-311+G(2d,2p) energetics at the HF/6-31G(d) geometries. For each dipeptide, both the N(delta)-H and N(epsilon)-H tautomers of the imidazole side chain of His were considered. For each of the four isomeric dipeptides, 20-30 conformers were fully characterized at the ab initio level. All low energy structures are found to involve H-bonding at the N(delta) position of imidazole, either as a N-H donor or a N acceptor, depending upon the tautomer. In three out of the four species, the most stable conformer involves a C-terminus carboxylic acid in its less favorable trans conformation, in order to maximize intramolecular H bonding. It turns out that the lowest energy tautomer of HisGly is N(epsilon)-H, while that of GlyHis is N(delta)-H. This result argues in favor of the diversity of His tautomeric states in peptides and proteins. The sodium cation complexes of both GlyHis and HisGly have been studied as well, again considering both tautomers in each case. In three out of the four species, the most stable structure involves chelation of sodium by the two carbonyl oxygens and the imidazole ring. On the contrary, the sodium complex of the N(delta)-H tautomer of HisGly favors chelation to the peptidic carbonyl oxygen, the imidazole ring and the amino terminus. In the N(epsilon)-H tautomers of both peptides, the most favorable binding site of imidazole is the N(delta) nitrogen, while in the N(delta)-H tautomers, it is the pi cloud which provides side chain interaction. As a result, both GlyHisNa+ and HisGlyNa+ favor the N(epsilon)-H tautomer of His, in contrast to what was found for the free peptides.

Ligand Exchange Reactions of Sodium Cation Complexes Examined Using Guided Ion Beam Mass Spectrometry: Relative and Absolute Dissociation Free Energies and Entropies

Guided ion beam mass spectrometry is used to study the ligand exchange reactions of Na+L1 with L2, where L1, L2 = H2O, C6H6, CH3OH, CH3OCH3, NH3, and C2H5OH, as a function of kinetic energy. For the endothermic ligand exchange reactions, reaction endothermicities are obtained by analyzing the kinetic energy dependence of the cross sections using our empirical threshold modeling equation. The thresholds are found to be systematically higher than values previously determined using competitive CID experiments by 0.07−0.2 eV. An analysis of the endothermic cross sections using a bimolecular, polyatomic phase theory model and a competitive, bimolecular RRKM model demonstrates that the systematic deviations result from a competitive shift between the thermoneutral reactions back to the reactants and the endothermic reactions to the ligand exchange products. For all reactions, thermal rate constants, k(298), are determined by modeling the cross sections in the low-energy region and integrating the model over a M...

Electron Spin Resonance Studies of Kinetic Effects of Substituent and Crown Ether on Intramolecular Sodium Cation Exchange in 2,5-Di-Tert-Amyl- and 2,5-Di-Tert-Butyl-1,4-Benzoquinone Radical Anions

Abstract Upon an addition of crown ethers to a solution of 2,5-di-tert-amyl-1,4-benzoquinone (2,5-DAQ) and 2,5-di-tert-butyl-1,4-benzoquinone (2,5-DBQ) radical anions, the significant broadening of the two-center lines was observed in their electron spin resonance (ESR) spectra. The formation constants for the complexation of sodium cation with three kinds of crown ethers in 2,5-DAQ and 2,5-DBQ radical ion pairs were estimated, and the intramolecular two-site jumping rates of sodium cation complexed with crown ethers were determined. Differential effects of steric and crown ether were found in the intramolecular sodium cation migration. The stabilization of inclusion complex of sodium cation with crown ethers gives rise to the acceleration effects on the rates of intramolecular migration of cation/crown-ether complex. Based on the results, a kinetic explanation for the intramolecular sodium cation migration in the presence of crown ethers was given.

Correlation Analysis of the Solvent Effects on the Thermodynamic Functions of Complexation of Sodium and Potassium Ions with 18-Crown-6 Ether in Aqueous-Organic Solvents

The effect of dielectric and chemical (donor-acceptor interactions, cohesion energy density) properties of aqueous-organic solvents (water-methanol, water-2-propanol, water-acetonitrile, water-acetone, water-dioxane) on the thermodynamic functions of complexation of sodium and potassium cations with 18-crown-6 ether at 298 K was subjected to overall correlation analysis.

Sodium cation complexation behavior of the heteroaromatic sidechains of histidine and tryptophan.

Three of the four essential amino acids that have aromatic sidechains exhibit cation-pi interactions with Na+ or K+; histidine does not and is shown here to be a sigma donor.

Relative and absolute bond dissociation energies of sodium cation complexes determined using competitive collision-induced dissociation experiments

Absolute L1Na+L2 and relative Na+-L bond dissociation energies are determined experimentally by competitive collision-induced dissociation of L1Na+L2 complexes with xenon in a guided ion beam mass spectrometer. The ligands examined include H2O, C6H6, CH3OH, CH3OCH3, NH3, and C2H5OH, which cover a range in Na+ affinities of only 20 kJ/mol. Dissociation cross sections for formation of Na+L1 + L2 and Na+L2 + L1 are simultaneously analyzed with a model that uses statistical theory to predict the energy dependent branching ratio. The use of independent and common scaling factors for each channel in this analysis is evaluated and discussed, as is the importance of properly handling ligand internal rotors. The cross section thresholds thus determined are interpreted to yield the 0 K L1Na+L2 bond dissociation energies and the relative 0 K Na+L binding affinities. The relative binding affinities are converted to absolute 0 K Na+L binding energies by using the absolute bond energy for Na+NH3, determined previously in our laboratory, as an anchor value. Comparisons are made to previous experimental and theoretical Na+L thermochemistry from several sources. The absolute L1Na+L2 bond dissociation energies were also calculated using ab initio theory at the MP2(full)/6-311+G(2d,2p)//MP2(full)/6-31G∗ level (corrected for zero-point energies and basis set superposition errors) and are in good agreement with the experimentally determined values.

Solid state network formation in arene-Sidearmed lariat ether complexes: contrasting behavior of sodium, potassium, and calcium cation complexes

Studies of lariat ether receptor systems and their complexes are reported. The receptors afford signficantly different complexes with similarly sized divalent calcium and monovalent sodium ions. Certain of the receptor-cation complexes form infinite networks in the solid state.

Preparation of Azulenequinones Containing Azacrown Moieties and the Singular Complexation of Sodium or Potassium Cation by 3,5-Bis(aza-18-crown-6)-1,7-azulenequinone in Solution

Preparation of Azulenequinones Containing Azacrown Moieties and the Singular Complexation of Sodium or Potassium Cation by 3,5-Bis(aza-18-crown-6)-1,7-azulenequinone in Solution

Investigation of Complexation of Sodium Cation by Anthracene Crown Ethers

Formation constants for complexes of sodium and anthracene crown ethers were determined using spectrophotometry and cyclic voltammetry. The complexation properties of the ligands examined depend significantly on alkyl substituents at 9 and 10-positions of the anthracene group and are strongly influenced by the solvent.

Complexation of Li +, Na +, and K + by water and ammonia

The energetics of complexation and the resulting polarization of solvent molecules were investigated for complexation of lithium, sodium, and potassium cations with water and with ammonia molecules. The mono-, di-, and tri-complexes were investigated using a double-zeta, polarized, diffuse, and balanced basis at both the molecular and atomic levels, using subsystem quantum mechanics. The stabilization at the molecular level during complexation results from large gains in the attractive energies overcoming the increases in repulsion. The cation–solvent interactions are closed-shell and involve only small transfers of electronic charge to the cations. On the atomic level, the cations are stabilized by inter-atom attraction, whereas the heavy atoms of the solvent molecules are destabilized by a small withdrawal of charge to the cation. Additional solvation continues to stabilize the cations, but each additional solvent molecule is less stabilized because of competition among solvent molecules. The solvent molecules are dipole polarized by a transfer of electronic charge from the bonded hydrogen atoms towards the heavy atom, a polarization that decreases with each additional solvent molecule and with increasing cation size.

Sodium cation complexation in a macrocycle containing thymines as sidearm donor groups

Previous studies of macrocycles having alkyl sidearms terminated in adenine or thymine have been focused on intermolecular association. Electrospray mass spectrometric analyses suggested that sodium complexation could be a major alternative process in the presence of the appropriate cation. Sodium cation complexation by N,N′-bis(3-(1-thyminyl)propyl)-4,13-diaza-18-crown-6 has been confirmed by X-ray crystallographic analysis. A sodium cation is bound in the center of the macroring. The four ether oxygens and two thyminyl carbonyl donors have the shortest contacts with the two, macroring nitrogen atoms being somewhat more remote. Neither the iodide counterion nor an acetone of solvation appears to interact with the sodium cation. Crystal Data: Triclinic, \(P_{\bar 1} \) , a = 11.9371(12), b = 12.1588(13), c = 13.7885(14) A, α = 78.083(2)°, β = 83.213(2)°, γ = 78.997(2)°, and Dcalc = 1.392 g cm−3, Z = 2.

Steric and Stereoelectronic Effects in Aza Crown Ether Complexes[1

Stability constants and enthalpy changes determined by calorimetric titrations and supported by selected NMR titrations are reported for the complexation of sodium and potassium cations with 18 different crown ethers containing nitrogen atoms with different number, location and substitution pattern. The data, measured in methanol mostly with potassium salts, are compared to literature data; they show striking differences between all-oxygen analogs and the macrocycles with NH groups. In contrast, affinities with aza crown ethers bearing alkyl groups at the nitrogen as well as with the cryptand [2.2.2] come closer to the complexation free energies predicted from the number and electron donating capacity of the ligand heteroatoms. This is rationalised on the basis of molecular mechanics calculations, showing that a NH-containing crown predominates in conformations with axial N lone pairs, due to their repulsive electrostatic interactions with the ring oxygen atoms. Replacement of the hydrogen by alkyl groups forces the lone pairs to an equatorial position, thus enabling better complex formation, as borne out by experiment. In line with these arguments the lgK differences are with some exceptions more due to ΔH than to TΔS differences. The calorimetric data show linear isoequilibrium correlations between TΔS and ΔH, with slopes between those observed with other crown ether and cryptand complexes. Preliminary investigations of some synthetic macrocyclic amide precursors yield appreciable complexation only, if the two carbonyl oxygens can come in close contact with the guest cation. Computer aided molecular modelling shows that this is possible in a small 15C5-derivative, in which the polyethylenglycol cycle only serves as ring template without binding contributions from the ether oxygen atoms.