Alkylation of salts ofN-(β-hydroxyalkyl)-N′-hydroxydiazeneN-oxides with alkyl halides and dimethyl sulfate

Salts ofN-(β-hydroxyalkyl)-N′-hydroxydiazeneN-oxides, RCH(OH)CH₂N(O)=NO⁻ M⁺ (R=Me, Prⁱ, or Bu^t; and M=Li, Na, K, Ag, NH₄, or Me₄N), were prepared. Their alkylation with alkyl halides R′X (X=Cl, Br, or I) and dimethyl sulfate was studied. Generally, alkylation afforded mixtures ofN-(β-hydroxyalkyl)-N′-alkoxydiazeneN-oxides RCH(OH)CH₂N(O)=NOR′ andO-alkyl-N-(β-hydroxyalkyl)-N-nitrosohydroxylamines RCH(OH)CH₂N(NO)OR′. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1996–2001, October, 1998.     

Protolytic properties and complexation with copper(II) ions of some azo derivatives of β-arylaminopropionic acids

The azo coupling reaction of N-(2-carboxyethyl)anthranilic acid and N,N,N′,N′-tetrabis(2-carboxyethyl)-1,3-phenylenediamine with diazosulfanilic acid yielded the complexones sodium 4-N-(2-carboxyethyl)amino-5-carboxyazobenzene-4′-sulfonate (I) and 2,4-N,N,N′,N′-tetrabis(2-carboxyethyl)diaminoazobenzene-4′-sulfonic acid (II), respectively. The acidity constants of I and II (20°C, μ = 0.1M KCl) were determined to be as follows: for I, pK ₀₀ = 1.29 ± 0.13, pK ₀ = 2.92 ± 0.07, pK ₁ = 3.92 ± 0.05, pK ₂ = 5.16 ± 0.03; for II, pK ₀₀ = 2.35 ± 0.06, pK ₀ = 2.81 ± 0.09, pK ₁ = 3.21 ± 0.11, pK ₂ = 3.81 ± 0.09, pK ₃ = 4.34 ± 0.04, pK ₄ = 5.03 ± 0.06, pK ₅ = 6.67 ± 0.07. The electronic absorption spectra of I and II were measured, and acid-base equilibrium scheme for I and II in aqueous solutions were suggested. The complexation constants of I and II with copper(II) ions were determined to be logK _CuQ^I= 5.47 ± 0.06 and logK _CuQ^II= 5.72 ± 0.13 (20°C, μ = 0.1 M KCl).     

Acenaphthylene-1,2-diamine radical cation. Molecular structure of the [(dpp-BIAN)H2]·+[X]− complex ((dpp-BIAN)H2 is N,N′-bis(2,6-diisopropylphenyl)-acenaphthylene-1,2-diamine; X = Cl or I)

Oxidation of N,N′-bis(2,6-diisopropylphenyl)acenaphthylene-1,2-diamine (dpp-BIAN)H₂ with silicon tetrachloride or mercury(II) chloride affords the [(dpp-BIAN)H₂]·⁺[Cl]⁻ compound. The corresponding iodine derivative, [(dpp-BIAN)H₂]·⁺[I]⁻, was prepared by hydrolysis of the reaction products of the magnesium complex (dpp-BIAN)Mg(THF)₃ with tetraiodosilane. X-ray diffraction study demonstrated that the [(dpp-BIAN)H₂]^·+ radical cation in these compounds chelates the corresponding halide anion. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 436–440, March, 2006.     

A thermodynamic study of complex formation between dicyclohexyl-18-crown-6 (DCH18C6) and La3+, UO 22+ , Ag+, and NH 4+ cations in acetonitrile-tetrahydrofuran binary media using conductometric method

The complex formation between La³⁺, UO₂²⁺ Ag⁺, and NH₄⁺ cations and macrocyclic ligand, dicyclohexyl-18-crown-6 (DCH18C6), was studied in acetonitrile-tetrahydrofuran (AN-THF) binary mixtures at different temperatures using the conductometric method. The results show that with the exception of complexation of the NH₄⁺ cation with DCH18C6 in pure acetonitrile, the stoichiometry of all the complexes is being 1: 1 (M: L). The stability constants of the complexes were determined using a GENPLOT computer program. The nonlinear behavior which was observed for changes of log K _f of the complexes versus the composition of the mixed solvent was discussed in terms of solvent-solvent interaction in their binary solution, which results in changing the chemical and physical properties of the constituent solvents when they mix with one another and, therefore, changing the solvation capacities of the metal cations, crown ether molecules, and even the resulting complexes with changing the mixed solvent composition. The results show that the selectivity of DCH18C6 for the studied cations changes with the composition of the AN-THF binary system. The sequence of stabilities of complexes in an AN-THF binary solution (mol. % AN = 75.0) at 25°C is [(DCH18C6)La)]³⁺ > [(DCH18C6)UO₂]²⁺ > [(DCH18C6)Ag]⁺ ∼ [(DCH18C6)NH₄]⁺, but in the case of other binary systems of AN/THF (mol. % AN = 25.0 and 50.0) is [(DCH18C6)La]⁺ > [(DCH18C6)NH₄]⁺ ∼ [DCH18C6)UO₂]²⁺ > [(DCH18C6)Ag]⁺. The text was submitted by the authors in English.     

New chromium(III)–picolinamide complexes. Kinetics and mechanism of picolinamide liberation in HClO4 solutions

Two new chromium(III) complexes with picolinamide (pica) and oxalates, [Cr(C₂O₄)₂(N,N′-pica)]²⁻ and [Cr(C₂O₄)₂(N,O-pica)]⁻, were obtained and the kinetics of their aquation in HClO₄ solutions were studied. The aquation leads to pica liberation and proceeds in two stages: (i) the chelate-ring opening at the Cr–amide bond and (ii) the Cr–N-pyridine bond breaking, which gives free pica and cis-[Cr(C₂O₄)₂(H₂O₂)₂]⁻. In the case of N,N′-bonded pica the kinetics of both stages was determined and in the case of the N,O-bonded pica only the second stage was investigated. The following rate laws were established: (k _obs)₁ = k ₀ + k ₁ Q ₁[H⁺] and (k _obs)₂ = k ₂ Q ₂[H⁺], where k ₀ and k ₁ are the rate constants of the chelate-ring opening in the unprotonated and protonated starting complex, and k ₂ is the rate constant of the pica liberation from the protonated intermediate. Kinetic parameters are calculated and the aquation mechanism is discussed.     

Palladium(II) complexes with R2edda-derived ligands. Part V. Reaction of O,O′-diethyl-(S,S)-ethylenediamine-N,N′-di-2-(3-methyl)butanoate with K2[PdCl4]

The reaction of K₂[PdCl₄] with [(S,S)-H₂(Et)₂eddv]Cl₂ diester (O,O′-diethyl-(S,S)-ethylenediamine-N,N′-di-2-(3-methyl)butanoate) (1) resulted in [PdCl₂{(S,S)-(Et)eddv-κ² N,N′,κO}] (2) complex with one hydrolyzed ester group. The compound was characterized by spectroscopic methods and it was found that the reaction is diastereoselective (¹H and ¹³C NMR; one diastereoisomer of four possible). In addition, the structure of 2 was confirmed by X-ray diffraction analysis, indicating that the product is the (R,R)–N,N′-configured isomer. DFT calculations support the formation of one diastereoisomer of 2.     

Tetraalkylammonium Picrates in the Dichloromethane–Water System: Ion-Pair Formation and Liquid–Liquid Distribution of Free Ions and Ion Pairs

Equilibria concerning picrates of tetraalkylammonium ions (Me₄N⁺, Et₄N⁺, Pr₄N⁺, Bu₄N⁺, Bu₃MeN⁺) in a dichloromethane−water system have been investigated at 25 ^∘C. The 1:1 ion-pair formation constants (K _IP,o ^o) in dichloromethane at infinite dilution were conductometrically determined. The distribution constants (K _D ^o) of the ion pairs and the free cations between the solvents were determined by a batch-extraction method. The K _IP,o ^o value varies in the cation sequence, Bu₄N⁺ ≈ Pr₄N⁺ ≈ Et₄N⁺ < Bu₃MeN⁺ < < Me₄N⁺; this trend is explained by the electrostatic cation−anion interaction taking into account the structures of the ion pairs determined by density functional theory calculations. For the ion pairs of the symmetric R₄N⁺ cations, there is a linear positive relationship between log₁₀ K _D ^o and the number of methylene groups in the cation (N _{CH 2}). The ion pair of asymmetric Bu₃MeN⁺ has a higher distribution constant than that expected from the above log₁₀ K _D ^o versus N _{CH 2} relationship. These cation dependencies of log₁₀ K _D ^o for the ion pairs are explained theoretically by using the Hildebrand-Scatchard equation. For all the cations, the log₁₀ K _D ^o value of the free cation increases linearly with N _{CH 2}; the variation of log₁₀ K _D ^o is discussed by decomposing the distribution constant into the Born-type electrostatic contribution and the non-Born one, and attributed to the latter that is governed by the differences in the molar volumes of the cations. The cation dependencies of the ion-pair extractability and ion pairing in water are also discussed. An erratum to this article can be found at     

Solvent extraction of calcium and strontium into nitrobenzene by using a synergistic mixture of hydrogen dicarbollylcobaltate and N,N,N′,N′-tetraisobutyl-2,6-dipicolinamide

Extraction of microamounts of calcium and strontium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H⁺B⁻) in the presence of N,N,N′,N′-tetraisobutyl-2,6-dipicolinamide [T(iBu)DPA, L] has been investigated. The equilibrium data have been explained assuming that the species HL⁺, HL₂ ⁺, CaL₂ ²⁺, SrL₂ ²⁺ and SrL₃ ²⁺ are extracted into the organic phase. The values of extraction and stability constants of the cationic complexes in nitrobenzene saturated with water have been determined.     

Solvent Effects on Ion-Pair Distribution and Dimerization of Tetraalkylammonium Salts

Summary.  The distribution of tetraalkylammonium ions (C _n H _2n+1 )₄N⁺ (R ⁺, TAAn ⁺, n = 4–7) with picrate ion (pic ⁻) and inorganic anions X ⁻, (Cl⁻, Br⁻, ClO⁻ ₄), into various inert organic solvents was studied at 25.0°C. The distribution data were analyzed by taking into consideration the distribution of ion pairs, R ⁺ · X ⁻, and the dimerization of the ion pairs, (R ⁺ · X ⁻)₂, in the organic phase. The ion-pair, distribution constant, K _dist, increases with increasing chain length of the tetraalkylammonium ion and with increasing ionic radius of the anion. The values of K _dist show a good correlation with the E _T value of solvent, i.e. the solvation ability with respect to the anion, and smoothly increase with increasing E _T. The effect of the solvent on the dimerization constants, K _dim, is markedly different between the ion pairs of picrate ion and inorganic anions. In the case of picrate, K _dim significantly decreases with decreasing length of the alkyl chain of the tetraalkylammonium ion, but hardly changes by changing the solvent. On the other hand, in the case of ion pairs of inorganic anions the value of K _dim decreases with decreasing E _T and is almost constant for all anions. These results were reasonably explained by the difference of the solvation of the anion moieties of the monomeric and dimeric ion pairs. Received May 15, 2001. Accepted (revised) July 18, 2001     

Effect of ligand on the redox reactions of thallium metal clusters

Pulse radiolysis of an aqueous solution of mono-valent thallium ion and mixed solutions of Tl⁺/Ag⁺ in the presence of various amino polycarboxylic acids such as trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid (DCTA), diethylenetriaminepentaacetic acid (DTPA), N-(2-hydroxyethyl)ethylenediaminetriacetic acid (HEDTA) and triethylenetetraminehexaacetic acid (TTHA) has been carried out. Abnormal valence states of Tl ions were generated. It is concluded that DCTA, DTPA, HEDTA and TTHA decrease the redox potential of Tl ions in aqueous solutions. It was observed that the electron transfer from complexed Tl₂⁺ to Ag⁺ varied in the range 7.5 × 10⁸ to 1.0 × 10⁹, depending on the type of complexing ligand. Electron transfer from Tl₂⁺ to Ag⁺ lead to the formation of silver atoms, which agglomerate further to form silver colloid.     

Kinetics and mechanism of oxidation of <Emphasis Type="Italic">N</Emphasis>-methylethylamine by bis(hydrogenperiodato)argentate(III) complex anion

Oxidation of N-methylethylamine by bis(hydrogenperiodato)argentate(III) ([Ag(HIO₆)₂]⁵⁻) in alkaline medium results in demethylation, giving rise to formaldehyde and ethylamine as the oxidation products. The oxidation kinetics has been followed spectrophotometrically in the temperature range of 20.0–35.0 °C, and shows an overall second-order character: being first-order with respect to both Ag(III) and N-methylethylamine. The observed second-order rate constants k′ increase with increasing [OH⁻] of the reaction medium, but decrease with increasing the total concentration of periodate. An empirical rate expression for k′ has been derived as: k′ = (k _a + k _b[OH⁻])K ₁/{f([OH⁻])[IO₄ ⁻]_tot + K ₁}, where k _a and k _b are rate parameters, and K ₁ is an equilibrium constant. These parameters have been evaluated at all the temperatures studied, enabling calculation of activation parameters. A reaction mechanism is suggested to involve two pre-equilibria, leading to formation of an intermediate Ag(III) complex, namely [Ag(HIO₆)(OH)(MeNHEt)]²⁻. In the subsequent rate-determining steps, this intermediate undergoes inner-sphere electron transfer from the coordinated amine to the metal center via two distinct routes, one of which is spontaneous while the other is mediated by a hydroxide ion.     

Synthesis, charge-separated state characterization of N-methyl-2-(4′-N-ethylcarbozole)-3-fulleropyrrolidine and its derivatives

N-Methyl-2-(N-ethylcarbozole)-fulleropyrro lidine and N-methyl-2-(4′-N,N-diphenylaminophenyl)-fulleropyrrolidine were synthesized by 1,3-dipolar cycloaddition under microwave irradiation, which were characterized by MS, ¹H NMR, IR and UV-Vis. Photoinduced intramolecular electron transfer process from C₆₀ moiety to carbazole moiety has been studied by nanosecond laser flash photolysis. The charge-separated state C₆₀ ^•−-Cz^•+ was observed in the near-IR region with a lifetime of 0.28 μs. The electronic spectrum of the C₆₀-TPA was studied by using ZINDO method on the basis of the optimized geometrics with B3LYP/6-31G* program. The results show that the calculated absorption was beyond 440nm, essentially consistent with the experimental value 433 nm. __________ Translated from Acta Chimica Sinica, 2005,63(17)(in Chinese)     

Synthesis and crystal structure of tris[(dibenzo-18-crown-6-(tetrahydrofuran)potassium) hexakis(isothiocyanato)ferrate(III) 0.3 hydrate

Abstrac  A new complex [K(Db18C6)(THF)]₃⁺[Fe(NCS)₆]³⁻ · 0.31 H₂O (I) was prepared and studied by X-ray diffraction (space group C2/c, a = 21.954, b = 26.496, c = 15.902 ?, β = 102.24°, Z = 4; direct method, leastsquares refinement in the anisotropic approximation to R = 0.098 for 5944 independent reflections; CAD4 automated diffractometer, λMoK _α). The [Fe(NCS)₆]³⁻ anion (on twofold axis) having a slightly distorted octahedral structure is connected by two K-S bonds with two complex cations connected by a twofold axis. Two independent complex cations [K(Db18C6)(THF)]⁺ are of the host-guest type, one being statistically disordered with respect to the twofold axis with site populations of 0.5. The coordination polyhedra of K⁺ are a distorted hexagonal bipyramid and pyramid. Original Russian Text ? A.N. Chekhlov, 2009, published in Koordinatsionnaya Khimiya, 2009, Vol. 35, No. 2, pp. 151–154.     

Mathematische und experimentelle Studien an wiederholten Auszügen aus Adsorptionssystemen,die sich im Gleichgewicht befinden,II

Zusammenfassung Die an den in einer vorangehenden Abhandlung aufgestellten Gleichungen der wiederholten Auszüge x^p=(x₀ ^p- K) (1−r)^pq+K (A) oder x^p=A_x(1−r)^pq+K (a)θ ^p=θ ₀ ^p −K _θ )(1−r)^pq+K _θ (B) oderθ ^p=A _θ (1−r)^pq+K _θ (b) angestellten überlegungen betrafen unter anderem die Bestimmung der Parameter A_x, A _θ , K und K _θ durch graphische Darstellung. Es wurde auch der auf die Werte von K und K _θ ausgeübte Einflu?, der durch ?nderung von m, der Menge des Adsorbenten, und von V, des Volumens der L?sung, infolge einer ?nderung in der quantitativen Zusammensetzung des Systems entstand, er?rtert. Es wurde auf die Verkleinerung von K und K _θ , die nach einer gewissen Zahl von Auszügen infolge einer zu starken Verdünnung der L?sung des Systems eintreten mu?, aufmerksam gemacht. Diese Verkleinerung erkl?rt sich aus der Anwesenheit des Koeffizienten a und des Exponenten n der Adsorptionsisotherme in den Gleichungen ; denn die beiden Werte von α und n sind nur für einen beschr?nkten Konzentrationsbereich praktisch konstant. Es wurde auch gefunden, da? die Werte vonθ, der Substanzmenge in L?sung, oder von x, der Konzentration in 1 ccm, die nach einem Auszug einer beliebigen Ordnung bestimmt wurden, den Gleichungen (b) und (a) für die Werte p′ von p, die andere sind als der zum untersuchten System geh?rende Wert, genügen unter der Bedingung, für K, K _θ , A_x und A _θ angemessene Werte zu finden. Die oben erw?hnte Schlu?folgerung gilt auch für p=1. Man erh?lt die beiden Gleichungen x=A′(1−r)^q+ K′ (E)θ=A (1−r)^q+K′θ, (F) die x undθ, die einer Auszugsordnung q entsprechen, direkt ergeben. Die Parameter A′, A, K′ und K′θ k?nnen graphisch ermittelt werden. Multipliziert man die Gleichung (F) mit r, dem bei dem Auszug entnommenen Volumteil, so erh?lt man die dem System durch einen Auszug entzogene Substanzmenge a_q: a_q=rA(1−r)^q−1+ c, (G) wo c=rK′θ. Am Schlu? der Abhandlung wird auf bestimmte Vorteile der Gleichungen (F) und (G) aufmerksam gemacht. I. Teil: Kolloid-Z.66, 322 (1934). übersetzt von E. Lottermoser (Leipzig).     

The glycosyl C1′—N9 bond of deoxyadenosine and deoxyguanosine: response to electrophilic attacks on the purinic nitrogen atoms

Self-consistent-field computations shed light on two relevant conformations of deoxyadenosine (dA) and deoxyguanosine (dG): one with a pseudoequatorial C_1′N₉ glycosyl bond and the other, a slightly more stable one, with its C_1′N₉ bond in a bisectional orientation. In dA, both the N₃ and N₇ nitrogens are plausible sites for electrophilic attack, but only N₇ is a plausible site in dG. The addition of H⁺, CH₃ ⁺, C₂H₅ ⁺ or tert-C₄H₉ ⁺ onto N₇ does not provoke notable structural modifications and leaves the base of dA and dG in an antiperiplanar (or nearly antiperiplanar) position with respect to the sugar C_1′O_4′ bond, but N₃ additions cause the base to adopt a synperiplanar or strongly chiral position. This produces strong interactions between the purine and deoxyribose moieties, whose relief could aid the eventual cleavage of the glycosyl bond of dA. Addition of a radical cation onto N₇ reduces the dissociation energy of the glycosyl bond by an estimated 8 kcal mol⁻¹ in dA and 4 kcal mol⁻¹ in dG – a bond weakening likely to concur to a depurination of DNA induced by radical cations. Received: 13 September 1999 / Accepted: 3 February 2000 / Published online: 21 June 2000     

Synthesis and crystal structure of [Et<Subscript>4</Subscript>N] [Cr(PzTp)Cl<Subscript>3</Subscript>] [PzTp<Superscript>−</Superscript> = Tetra(pyrazolyl) Borate]

Treatment of CrCl₃(THF)₃ with KPzTp in THF affords of the compound K[Cr(PzTp)Cl₃], and the K⁺ in this complex can be replaced by Et₄N⁺ in CH₂Cl₂. Well-defined green crystals of [Et₄N]r(PzTp)Cl₃] (I) suitable for X-ray diffraction are obtained at −₂0°C. In the anion the metal center shows a distorted octahedral geometry with the tetra(pyrazolyl) borate bonded as three N-donor tripod ligands and three chloride atoms completing the coordination sphere.     

Complexation of 4′-Nitrobenzo-15-crown-5 with Zn<Superscript>2+</Superscript>, Mn<Superscript>2+</Superscript>, Cr<Superscript>3+</Superscript> and Sn<Superscript>4+</Superscript> Cations in Acetonitrile–Ethanol Binary Mixtures

The complexation reactions of 4′-nitrobenzo-15-crown-5 (4′NB15C5) with Zn²⁺, Mn²⁺, Cr³⁺ and Sn⁴⁺ cations were studied in acetonitrile–ethanol (AN–EtOH) binary solvent mixtures at different temperatures by the electrical conductometry method. The stability constants of the resulting 1:1 complexes were determined from computer fitting of the conductance versus mole ratio data. The results show that the selectivity order of 4′NB15C5 for the metal cations in the AN–EtOH (mol-%AN=76) binary solvent at 298.15 K is: Cr³⁺>Mn²⁺≈Zn²⁺>Sn⁴⁺, but the selectivity order changes with the composition of the mixed solvents. A nonlinear relationship was observed between the stability constants (log ₁₀ K _f) of these complexes and the composition of the AN–EtOH binary solvents. The corresponding thermodynamic parameters (DH_c^o, DS_c^o)(\Delta H_{\mathrm{c}}^{\mathrm{o}}, \Delta S_{\mathrm{c}}^{\mathrm{o}}) were obtained from the temperature dependence of the stability constants using van’t Hoff plots. The results show that the values and also the sign of these parameters are influenced by the nature and composition of the mixed solvents.     

Spectroscopic study of protonation of oligonucleotides containing adenine and cytosine

Acidobasic properties of purine and pyrimidine bases (adenine, cytosine) and relevant nucleosides (adenosine, cytidine) were studied by means of glass-electrode potentiometry and the respective dissociation constants were determined under given experimental conditions (I = 0.1 M (NaCl), t = (25.0 ± 0.1) °C): adenine (pK _HL = 9.65 ± 0.04, pK _H2L = 4.18 ± 0.04), adenosine (pK _H2L = 3.59 ± 0.05), cytosine (pK _H2L = 4.56 ± 0.01), cytidine (pK _H2L = 4.16 ± 0.02). In addition, thermodynamic parameters for bases: adenine (ΔH ⁰ = (−17 ± 4) kJ mol⁻¹, ΔS ⁰ = (23 ± 13) J K⁻¹ mol⁻¹), cytosine (ΔH ⁰ = (−22 ± 1) kJ mol⁻¹, ΔS ⁰ = (13 ± 5) J K⁻¹ mol⁻¹) were calculated. Acidobasic behavior of oligonucleotides (5′CAC-CAC-CAC3′ = (CAC)₃, 5′AAA-CCC-CCC3′ = A₃C₆, 5′CCC-AAA-CCC3′ = C₃A₃C₃) was studied under the same experimental conditions by molecular absorption spectroscopy. pH-dependent spectral datasets were analyzed by means of advanced chemometric techniques (EFA, MCR-ALS) and the presence of hemiprotonated species concerning (C⁺-C) a non-canonical pair (i-motif) in titled oligonucleotides was proposed in order to explain experimental data obtained according to literature.     

CO<Subscript>2</Subscript> adsorption and dehydration behavior of LiNaX,KNaX, CaNaX and CeNaX zeolites

In this study, NaX synthetic zeolite was modified by following the conventional cation exchange method at 70°C. 82, 81, 79 and 48% of sodium were exchanged with Li⁺, K⁺, Ca2⁺ and Ce3⁺, respectively. Thermal analysis data obtained by TG/DSC was used to evaluate the dehydration behavior of the zeolites. The strongest interaction with water and the highest dehydration enthalpy (ΔH) value were found for Li-exchanged form and compared with the other forms. The temperature required for complete dehydration increased with decreasing cation size (cation size: K⁺>Ce³⁺>Ca2⁺>Na⁺>Li⁺). CO₂ adsorption at 5 and 25°C was also studied and the virial model equation was used to analyze the experimental data to calculate the Henry’s law constant, K _o and isosteric heat of adsorption at zero loading Q _st. K _o values decreased with increasing temperature and the highest Qst was obtained for K rich zeolite. It was observed that both dehydration and CO₂ adsorption properties are related to cation introduced into zeolite structure.     

Solvent‐ and counterion‐specific swelling behavior of poly(acrylic acid) gels

The collapse of alkali metal poly(acrylate) (PAAM) gels was investigated for various water/organic solvent mixture systems: methanol (MeOH), ethanol (EtOH), 2‐propanol (2PrOH), t‐butanol (tBuOH), dimethyl sulfoxide (DMSO), acetonitrile (AcN), acetone, tetrahydrofuran (THF), and dioxane. In order to ascertain the counterion specificity in the swelling behavior, four kinds of alkali metal counterions were used: Li⁺, Na⁺, K⁺, and Cs⁺. Remarkable solvent and counterion specificities were observed for every counterion species and every solvent system, respectively. For example, in aqueous EtOH the dielectric constants (D_cr) at which collapse occurred were in the order PAACs < PAALi < PAAK < PAANa. On the other hand, the D_cr at which PAALi gel collapsed increased in the order tBuOH < dioxane < THF < MeOH < 2PrOH < EtOH < acetone < AcN < DMSO, where the D_cr ranged from about 39 to about 67. This was in contrast to our previous observation for a partially quaternized poly(4‐vinyl pyridine) (P4VP) gel, which collapsed in a much narrower D_cr region in similar mixed solvents. The present solvent‐ and counterion‐specific collapses are discussed on the basis of solvent properties such as the dielectric constant and Gutmann's donor number and acceptor number of a pure solvent. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2791–2800, 2000