Pitzer model parameters for sparingly soluble salts from solubility measurements. The systems TlCl+SrCl2+H2O and TlCl+BaCl2+H2O at 25°C

The solubility of thallium(I) chloride has been determined in aqueous solutions of strontium chloride and barium chloride at concentrations up to 1.5 mol kg^–1. The data were analyzed using Pitzer's equations without making explicit assumption of association to ion pairs by assuming =3 instead of =2, with the ⁽¹⁾ term for TlCl being equivalent to the ⁽²⁾ term for 2-2 electrolytes. Best values of ⁽⁰⁾ and ⁽¹⁾ for TlCl are recommended together with K _s , the activity solubility product. These were used to fit the present solubility data and derive the Pitzer model mixture parameters relevant to the systems, _fTIN and _fTINCl (N=Sr, Ba). Mixture parameters for TlCl+MCl+H₂O systems are also derived to complete the parameter base. The fit of the experimental data was found to be worse when higher-order terms for asymmetrical mixing were included in the analysis. Activity coefficients for thallium(I) chloride in the mixtures are derived.     

Cardiac glycosides of Cheiranthus allioni. IX

Summary From the seends ofCheiranthus allioni hort. another three cardiac glycosides have been isolated. One of them has been identified as cheirotoxin. It has been established that in cheirotoxin the D-glucose is attached to C₄ of the D-gulomethylose and this glycoside therefore has the structure of strophanthidin 3-O-[4-O--D-glucopyranosyl--D-gulomethylopyranoside]. The two other glycosides, which have been named sarmentogulomethyloside and gulosarmentoglucoside are new and are, respectively, sarmentogenin-3-O--D-gulomethylopyranoside and sarmentogenin 3-O-[4-O--D-glucopyranosyl--D-gulomethylopyranoside].For Communication VIII see [1].Khar'kov Scientific-Research Institute of Pharmaceutical Chemistry. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 607–611, September–October, 1974.     

Comparison of the Complexation of Cosmetical and Pharmaceutical Compounds with γ-Cyclodextrin, 2-Hydroxypropyl-β-cyclodextrin and Water-Soluble β-Cyclodextrin-co-epichlorhydrin Polymers

The ability of different cyclodextrins (CDs): CD, 2-hydroxypropyl CD to complex drugs like 3--hydroxy-11-oxoolean- 12-en-30-oic acid, 2-ethylhexyl-3-(4-methoxyphenyl)-2-propanoate and menthol was compared to that of water-soluble polymers: CD-co-epichlorhydrin polymer (pCD/EP) and CD-co-epichlorhydrin polymer partially modified with trimethylammonium groups (pCD/EPN⁺). 3--Hydroxy-11-oxoolean-12-en-30-oic acid was poorly solubilized by CD compared with other CD derivatives, however the determination of the complexation constants was possible for pCD/EP, K₁₁ = 740, K₁₂ = 4, for pCD/EPN⁺, K₁₁ = 681, for CD, K₁₁ = 16 and for hydroxypropyl CD, K₁₁ = 114, K₁₂ = 3.4. A significant increase of the solubility was observed for 2-ethylhexyl-3-(4-methoxyphenyl)-2-propanoate with all host molecules, it was 916 times its solubility in pure water with pCD/EPN⁺, 1116 and 1300 times with 2-hydroxypropyl CD and pCD/EP respectively. The association constants are K₁₁ = 7970, K₁₁ = 4700, K₁₁ = 1470, K₁₁ = 230 and K₁₂ = 200 with pCD/EP, pCD/EPN⁺, CD, 2-hydroxypropyl CD respectively. An increase of the solubility of menthol was observed with all CD derivatives, up to 36–37 times, except for CD. The complexation constants are similar equal to about 200.     

Polarographische Bestimmung der Stabilitätskonstanten ammoniakalischer Magnesiumkomplexe

Zusammenfassung Die polarographische Methode des Indikatorions wurde zur Untersuchung der Komplexbildung des Mg²⁺-Ions mit Ammoniak verwendet. Es wurden die Stabilitätskonstanten ₁,₂,₃,₄ und ein annähernder Wert für ₅ bestimmt.

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Investigation of stability constants of magnesium ion-ammonia complexes

The polarographic method with indicator ion was used for investigation of magnesium ion complexation with ammonia. The numerical values of the stability constants ₁,₂,₃,₄ and the approximative value of ₅ were determined.

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Mit 2 Abbildungen     

A molecular mechanics study of the effect of substitution in position 1 on the conformational space of the oxytocin/vasopressin ring

Summary The effect of the substitution in position 1 on the low-energy conformations of the oxytocin/vasopressin 20-membered ring was investigated by means of molecular mechanics. Three representative substitutions were considered: -mercapto-,-dimethyl)propionic acid (Dmp), (-mercapto-,-cyclopentamethylene)propionic acid (Cpp), both forming strong antagonists, and (,-dimethyl--mercapto)propionic acid (-Dmp), forming analogs of strongly reduced biological activity, with the -mercaptopropionic (Mpa) residue taken as reference. Both ECEPP/2 (rigid valence geometry) and AMBER (flexible valence geometry) force fields were employed in the calculations. Three basic types of backbone conformations were taken into account which are distinguished by the type of -turn at residues 3 and 4: 1/III, II, and I/III, all types containing one or two intra-annular hydrogen bonds. The allowed (ring-closed) disulfide-bridge conformations were searched by an algorithm formulated in terms of scanning the disulfide-bridge torsional angle C-S-S-C. The ECEPP/2 and AMBER energies of the obtained conformations were found to be in reasonable agreement. Two of the low-energy conformers of the [Mpa¹]-compound agreed very well with the cyclic part of the two conformers found in the crystal structure of [Mpa¹]-oxytocin. An analysis of the effect of -substitution on relative energies showed that the conformations with the N-C-CH₂-CH₂ (₁) and C-CH₂-CH₂-S (₁) angles of the first residue around (–100°, 60°) and (100°, –60°) are not affected; this in most cases implies a left-handed disulfide bridge. In the case of -substitution the allowed values of ₁ are close to ± 60°. This requirement, being in contradiction to the one concerning -substitution, could explain the very low biological activity of the -substituted analogs. The conformational preferences of substituted compounds can largely be explained by the analysis of local interactions within the first residue. Based on the selection of the conformations which are low in energy for both the reference and -substituted compounds, two distinct types of possible binding conformations were proposed, the first one being similar to the crystal conformer with a left-handed disulfide bridge, the second one having a right-handed bridge, but a geometry different from that of the crystal conformer with the right-handed bridge. The first type of disulfide-bridge arrangement is equally favorable for both I/III and II types of backbone structure, while the second one is allowed only for the II type of backbone. No conformation of the I/III type has a low enough energy to be considered as a possible binding conformation for all of the active compounds studied in this work.     

Complexing equilibria and redox potentials of the Ag(II)/Ag(I) system in the presence of 2,2′:6′,2″-terpyridine in water

Summary The conditional protonation constants (=0.1) for 2,2:6,2-terpyridine, logK ₁=4.93, logK ₂=3.69, were determined by thepH-metric method. The compositions of complexes of Ag²⁺ and Ag⁺ ions with 2,2:6,2-terpyridine (tp) were studied and equilibria of the complex formation process were described. The values of conditional complex formation constants are as follows: for Ag(tp) ₂ ⁺ :log₀₁=5.79, log₀₂=9.68, for Ag(tp) ₂ ²⁺ :log₀₂=25.31, while the conditional constant of the Ag(tp)NO₃ precipitate formation is:K _SO=2.45·10⁴. Using coulometric and chronovoltamperometric measurements, the redox systems being formed in the complex solutions of Ag(II) and Ag(I) were determined and described including their formal potentials.

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Komplexibildungsgleichgewichte und Redoxpotentiale des Systems Ag(II)/Ag(I) in Gegenwart von 2,2:6,2-Terpyridin in Wasser

Zusammenfassung Mit Hilfe derpH-metrischen Methode wurden die konditionalen Protonationskonstanten (=0.1) von 2,2:6,2-Terpyridin bestimmt: logK ₁=4.93, logK ₂=3.69. Es wurde auch die Zusammensetzung der Komplexe von Ag(II) und Ag(I) mit 2,2:6,2-Terpyridin(tp) bestimmt sowie die Gleichgewichte der komplexbildung beschrieben. Die Werte der Konditionalkomplexbildungskonstanten sind: für Ag(tp) ₂ ⁺ :log₀₁=5.79, log₀₂=9.68, für Ag(tp) ₂ ²⁺ :log₀₂=25.31 und für das Löslichkeitsprodukt Ag(tp)NO₃:K _SO ^–1 =4.08·10^–5. Die in Komplexlösungen von Ag(II) und Ag(I) vorliegenden Redoxsysteme wurden mittels cyclischer Voltametrie und Coulometrie untersucht und die Formalpotentialwerte dieser Systeme in Wasser bestimmt.

     

Controlled-potential coulometric studies on fluoride and sulphate complexes of neptunium (VI)

Fluoride and sulphate complexing of Np(VI) has been studied by controlled-potential coulometry at a constant ionic strength. The values of ₁ ^* and ₂ ^* for fluoride complexes were found to be 9.4 and 8.9, respectively, at an ionic strength =0.5. At an ionic strength =1.0, ₁ ^* and ₂ ^* obtained were 6.6 and 10.5, respectively. Sulphate complexing of Np(VI) was studied only at an ionic strength =0.5. The value of ₁ ^* obtained was 5.6.     

The crystal and molecular structure of the β-cyclodextrin inclusion complex with aspirin and salicylic acid

The crystal structure of the -cyclodextrin (-CyD) molecular complex with aspirin (acetylsalicylic acid), salicylic acid, and water, (C₄₂H₇₀O₃₅)₂ (C₉H₈O₄)₂ (C₇H₆O₃) 23.3H₂O, was determined by X-ray structure analysis. The crystal data is space group Pl, a=19.777(5), b=15.247(3), c=15.475(4) Å, =102.63(2)°, =116.96(2)°, =104.12(2)°, V=3729(2) ų, D_m=1.409(2) g/cm³, D_X=1.419 g/cm³, and Z=1. The two -CyDs form a dimer unit with hydrogen bond networks among the secondary hydroxyl groups of both -CyDs. This -CyD dimer includes three guest molecules of two different types in its hydrophobic cavity. Two of them are aspirin, which are separately included in each cavity of the -CyD unit, with their hydrophobic benzene rings protruding into the hydrophobic cavities of the host -CyDs. The remaining guest molecule is the hydrolyzed product of an aspirin, that is salicylic acid, which is sandwiched in the space constructed by the -CyD dimer formation, and is statistically disordered at three sites.     

1-Aryl-6-azauracile, 5. Mitt.: Die Synthese von 1-(β-Pyridyl)-6-azauracil-5-carbonsäure und einiger ihrer Derivate

Zusammenfassung Analog wie in vorherigen Mitteilungen^1–4 wurden -Pyridyl-hydrazono-cyanacetylcarbamidsäureäthylester (1), 1-(-Pyridyl)-5-cyan-6-azauracil (2), 1-(-Pyridyl)-6-azauracil-5-carbonsäure (3), deren Thioamid (4), und Amidoxim (5), welches in 1-(-Pyridyl)-5-[5-methyl-1,2,4-oxdiazolyl(3)]-6-azauracil (6) überge-führt wurde, hergestellt.

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-Pyridylhydrazono-cyanacetylcarbamic acid ethyl ester (1), l-(-pyridyl)-5-cyano-6-azauracil (2), 1-(-pyridyl)-6-azauracil-5-carboxylic acid (3), its thioamide (4) and amidoxime (5) were prepared as described in preceding communications. (5) was converted into l-(-pyridyl)-5-[5-methyl-1,2,4-oxdiazolyl(3)]-6-azauracil (6).

     

Thermodynamic properties of water-β-cyclodextrin-dodecylsurfactant ternary systems

Densities, heat capacities and conductivities of water-surfactant--cyclodextrin (-CD) ternary systems were determined at 25°C. The surfactants studied were sodium dodecylsulfate (NaDS) and dodecyltrimethylammonium bromide (DTAB). From conductivity data, apparent critical micelle concentrations (cmc^*) and degree of ionization of micelles were obtained at a fixed -CD concentration (m_CD). From the cmc^* value and that in water (cmc) the stoichiometry of the surfactant--CD complex was calculated. At a given m_CD, the apparent molar volume V_,CD and heat capacity C_,CD of -CD in the two surfactants were calculated as functions of surfactant concentration m_S. For both NaDS and DTAB, V_,CD increases with m_S up to about the cmc beyond which it decreases to a constant value at high m_S, the opposite is observed for C_,CD. With NaDS, a jump in the C_,CD vs, m_S trend was detected and ascribed to a structural NaDS micellar transition. The apparent molar volume V_S and heat capacity C_S of NaDS and DTAB in the water--CD mixture 0.017 m were also obtained. From these properties and those in pure water, the volume V_S and heat capacity C_S of transfer of the surfactant from water to water+-CD mixture as functions of m_S were calculated. For both surfactants, the V_S vs. m_S trends increase to the cmc and then decrease in a monotonic manner, whereas C_S increases regularly with m_S in the pre-micellar region and is essentially constant in the post-micellar region. The V_S vs. m_S trends were qualitatively explained in terms of dispersed, complexed and micellized surfactant contributions.     

Triterpene glycosides of Astragalus and their genins XLII. Cycloartanes of Astragalus tragacantha

Another six components ofAstragalus tragacantha Habl. have been identified on the basis of spectral characteristics and chemical transformations. We have previously described cyclocanthagenin and its 3-0--D-xylopyranoside — cyclocanthoside A — as products of the acid hydrolysis of cyclocanthoside D. Cyclocanthosides B, C, E, and G are here described for the first time and are (24S)-cycloartane-3,6,16,24,25-pentol 3-O-(4-O-acetyl--D-xylopyranoside) 6-O--D-glucopyranoside, (24S)-cycloartane-3,6,16,24,25-pentol 6-O-(6-O-acetyl--D-glucopyranoside) 3-O--D-xylopyranoside, (24S)-cycloartane-3,6, 16,24,25-pentol 6-O--D-glucopyranoside, and (24S)-cycloartane-3, 6, 16, 24, 25-pentol 6-O--D-glucopyranoside 3-O-[O--D-glucopyranosyl-(12)--D-xylopyranoside], respectively.Institute of Chemistry of Plant Substances, Uzbekistan Academy of Sciences, Tashkent. Institute of Ecological Genetics, Moldavian Academy of Sciences, Kishenev. Translated from Khimiya Prirodnykh Soedinenii, Nos. 3,4, pp. 360–367, May–August, 1992.     

Complexation of Vinpocetine with Cyclodextrins in the Presence or Absence of Polymers. Binary and Ternary Complexes Preparation and Characterization

Inclusion complexation between -cyclodextrin (-CD),hydroxypropyl--cyclodextrin (HP--CD), water-solublepolymers (PVP and HPMC) and vinpocetine was studied in aqueous solution and in the solid state.Phase solubility studies were used to evaluate the complexation in aqueous solution at roomtemperature. Stability constants (K_c) of binary and ternary complexes were determined spectrophotometrically. Differential scanning calorimetry (DSC)was used to characterize kneaded, co-evaporated and lyophilised binary and ternary systems.The K_c values obtained were 70.14 M^-1 and 35.01 M^-1 for vinpocetine--CD and vinpocetine-HP--CD and increased in a range of 17% to 94%by addition of water-soluble polymers. Some preliminary evidences ofinclusion complexation were obtained from DSC suggesting that co-evaporated and lyophilised binary andternary systems were truly inclusion complexes.     

Spectrophotometric study of Nd,Sm, and Ho complexation in chloride solutions at 100–250°C

Complex formation in Ln chloride solutions is studied by spectrophotometric method. Electronic absorption spectra of Nd³⁺, Sm³⁺, and Ho³⁺ ions are measured in the range of supersensitive transitions in solution with Cl^– ion concentration from 0 to 5 mol/l in 100–250°C temperature interval under saturated vapor pressure. The Nd and Sm spectra represent integrated curves that mainly consist of Ln³⁺ and LnCl²⁺ absorption bands (with stability constant ₁), while the Ho spectra consist of Ho³⁺ and HoCl ₂ ⁺ absorption bands (with ₂). The stability constants ₁ and ₂ calculated for each wave number by linear regression method acquire steady values and have the meaning of the best unbiased linear estimates. Thermodynamic values of log₁ for Nd, Sm, and Ho monochlorides lie in a narrow interval at constant temperature. In the case of Nd and Sm, the temperature curves of log₁ and log₂ have smaller slopes as compared to that of Ho, which is explained by the effect of a covalent component in their spectra that adds to the ionic nature of the bonds in monochloride complexes. The ₂ values increase in the order Nd相似文献   

Radiation-induced reactions of cholesterol in an aqueous medium

⁶⁰Co -ray radiolysis of cholesterol /3-hydroxy-5-cholestene/ /I/ in the two-phase system /water-ethyl acetate/ and in the presence of air has been studied using TLC and GC methods. The following products were observed in the irradiated mixture: 3, 7-dihydroxy-5-cholestene /II/, G O. 36, 3-hydroxy-7-keto-5-cholestene /III/, G 1.48, 3-hydroxy-7-keto-5-cholestane /IV/, G 0.22, 3,5,6-trihydroxy-5-cholestane /V/, G 0.83, 5,6-epoxy-3-hydroxy-5-cholestane /VIa/, G 0.26, 5,6-epoxy-3-hydroxy-5-cholestane /VIb/, G 0.24, and 2, 3-dihydroxy-5-cholestene /VII/, G 0.22. The dose dependence of the formation of these products shows that the cholesterol derivatives substituted in the position 7 /II–IV/ are formed from a common precursor — the radical Ia. On the other hand, the products of the 5–C=C double bond reactions /V and VI/ are formed independently. Also the product VII is formed independently. A reaction scheme that is in agreement with these results is proposed.     

Interaction of tri-O-methyl-β-cyclodextrin with drugs

Summary The effect of tri-O-methyl--cyclodextrin(methyl--CD) on the partition coefficients of drugs, such as p-nitrophenol, salicylic acid, benzoic acid, and aspirin, was studied at 25°C. The partition coefficients of these drugs were increased linearly with methyl--CD concentration. The increase of partition coefficients was interpreted by the 11 complex formation between methyl--CD and the drug in CHCl₃ phase.The interaction between p-nitrophenol and methyl--CD in solution was studied by UV and PMR spectroscopies. It was concluded that p-nitrophenol is included in the cavity of methyl--CD in both aqueous solution and CHCl₃ solution.Inclusion compounds of these drugs with methyl--CD in the solid state were studied by X-ray diffractometry, IR spectroscopy, and DSC measurements. 11 crystalline inclusion compounds were obtained from hot water. It is also suggested that amorphous inclusion compound was obtained by the grinding of drug with methyl--CD.The dissolution rate and the bioavailability of ketoprofen were significantly increased in the presence of methyl--CD. The bioavailability of ketoprofen after oral administration with methyl--CD to rats was 3.7 times that of ketoprofen alone.     

Stereoselective Hydrogenation of Thymol over Rh/alumina in the Presence of β:-cyclodextrin and its Derivatives

Stereoselective hydrogenation of thymol over Rh/alumina in the presence of various equivalents of -cyclodextrin (-CD) and itsderivatives in the solid state was studied. Hydrogenation of thymol in the absence of -CD gave 76.8% epimeric alcohols with a menthol/neomenthol (M/N) ratio of 5.6 and an alcohol/ketone ratio of 4.5, whereas the presence of 0.1 equivalent (to thymol) of -CD gave rise to 94.6% of epimeric alcohols with a M/N ratio of 6.3 and an alcohol/ketone ratio of 45.4. The effect of -cyclodextrin and its derivatives on the modification of the yield and the proportion of epimeric alcohols formed were found to be the salient features of this investigation. Inclusion complexation of thymol by -CD studied by UV-Visible spectroscopyindicated a 2:1 stoichiometry ofthymol: -CD complex with a binding constant value of 480 ±40 M^-2.     

Inclusion Complexes of Cyclodextrins with Tetrakis(4-carboxyphenyl)porphyrin and Tetrakis(4-sulfonatophenyl)porphyrin in Aqueous Solutions

In neutral and alkaline solutions, tetrakis(4-carboxyphenyl)porphyrin (TCPP) and tetrakis(4-sulfonatophenyl)porphyrin (TSPP) form 1:1 and 2:1 host–guest inclusion complexes with -cyclodextrin (-CD), -cyclodextrin (-CD), and 6-deoxy-6-diethylamino--CD (DEA--CD), except for DEA--CD in alkaline solution. On the other hand, TCPP and TSPP form only 1:1 inclusion complexes with 6-deoxy-6-dihexylamino--CD (DHA--CD). The limited solubilities of DEA--CD in alkaline solution and DHA--CD are likely responsible for no observation of the 2:1 inclusion complex containing DEA--CD in alkaline solution and that containing DHA--CD. The equilibrium constants (Ks) of TCPP and TSPP for the formation of the inclusion complexes have been estimated from the absorption and/or fluorescence intensity changes in neutral and alkaline solutions. The K₂ values, which are the equilibrium constants for the formation of the 2:1 host–guest inclusion complex from the 1:1 inclusion complex, are about one tenth the corresponding K₁ values, except for the -CD–TSPP system in alkaline solution. In neutral solution, where DEA--CD and DHA--CD are in protonated forms, the electrostatic force operates between DEA--CD (DHA--CD) and TCPP (TSPP), leading to the greater K values than those in alkaline solution, where DEA--CD and DHA--CD exist as neutral species.     

Improvement of Solubility and Dissolution of 19-Norprogesterone via Inclusion Complexation

In an effort to modify the solubility and dissolution rate of the contraceptive steroid, 19-norprogesterone in order to improve its bioavailability, the cyclodextrin complexation approach was chosen. In solution, the complex formation with -cyclodextrin (-CD), hydroxyethyl -cyclodextrin (HE--CD) and hydroxypropyl -cyclodextrin (HP--CD) was confirmed by using solubility, UV, IR and ¹H-NMR spectrophotometric techniques. The phase solubility diagrams were categorized as A_L-type. The complexing affinity of the CDs investigated were ranked as follows: -CD > HP--CD > HE--CD. The complexation thermodynamic parameters were obtained from the temperature dependence of the dissociation constants. In the solid state, differential scanning calorimetery (DSC) and optical microscopy methods were utilized to characterize the complexes. Dissolution studies showed that such molecularly encapsulated forms offered a marked improvement in the dissolution rate compared to the parent drug.     

Prediction of Stability Constants for Cr(III) and Cr(II) Complexes

Regression analysis was used to derive equations for estimaing thermodynamic stability constants for complexes of Cr²⁺ (log^° ₁[Cr²⁺L] = 0.53log^° _n [H _n L]) and Cr³⁺ (log^° ₁[Cr³⁺L] = 0.88log^° _n [H _n L]) from the known protonation constants of H _n L ligands and for determining stability constants of Cr²⁺ and Cr³⁺ complexes from the available stability constants of Cu²⁺ complexes (log^° ₁[Cr²⁺L] = 0.76log^° ₁[Cu²⁺L] and log^° ₁[Cr²⁺L] = 0.60log^° ₁[Cr³⁺L], respectively). Parameters of the Panteleon–Ecka equation for calculating stability constants of Cr²⁺ complexes ( = 0.57) and Cr³⁺ complexes ( = 0.69) with two and three bidentate ligands were also determined. The ratio of logarithmic stability constants for complexes with the same metals but with different metal ionic charges was found to be approximately equal to the ratio of charges on the central ions. The stability constant of Cr(II) sulfate complex was calculated.