Search results for "aqueous solution"
showing 10 items of 1610 documents
Oxalate and 2,2′-bipyrimidine as bis-chelating ligands in the honeycomb layered compound {[Fe2(bpym)(ox)2]·5H2O}n
2002
The novel two-dimensional iron(II) compound of formula {[Fe2(bpym)(ox)2]·5H2O}n (1) [bpym = 2,2′-bipyrimidine and ox = oxalate dianion] is obtained by reaction of oxalic acid, iron(II) chloride and 2,2′-bipyrimidine in aqueous solution. The structure of 1 is made up of oxalato-bridged iron(II) chains cross-linked by bischelating bpym affording a honeycomb lattice. Variable-temperature magnetic susceptibility data of 1 show the occurrence of relatively large antiferromagnetic interactions between the high spin iron(II) ions separated by more than 5.5 A through bridging bpym [Jbpym = −4.0(2) cm−1] and ox [Jox = ca. −7.8(2) cm−1] ligands. These values compare well with those obtained in the ir…
Copper(II)-assisted hydrolysis of 2,4,6-tris(2-pyrimidyl)-1,3,5-triazine (tpymt): syntheses, crystal structures and magnetic properties of [Cu(bpcam)…
2005
Abstract The reaction of the 2,4,6-tris(2-pyrimidyl)-1,3,5-triazine (tpymt) ligand with copper(II) perchlorate or sulfate in aqueous solution affords complexes [Cu(bpcam)(H2O)2]ClO4 · 3H2O (1), [Cu(bpcam)(H2O)2][Cu(bpcam)(H2O)(SO4)] · 2H2O (2) and [Cu2(bpcam)2(H2O)2(SO4)] · H2O (3) [bpcam = bis(2-pyrimidylcarbonyl)amidate], whose structures have been determined by single-crystal X-ray diffraction studies. Copper(II) promotes the hydrolysis of tpymt in mild conditions yielding the bpcam group which is present in the structures of 1–3 as a tridentate ligand. The structure of 1 consists of mononuclear [Cu(bpcam)(H2O)2]+ cations, uncoordinated perchlorate anions and water of crystallization. Th…
Correlation between hydrophobicity and retention data of several antihistamines in reversed-phase liquid chromatography with aqueous-organic and mice…
2000
Abstract The correlation between the retention of 12 antihistamines (carbinoxamine, chlorpheniramine, cyclizine, cyproheptadine, dexbrompheniramine, dexchlorpheniramine, diphenhydramine, doxylamine, pheniramine, phenyltoloxamine, pyrilamine and tripelennamine), in reversed-phase liquid chromatography (RPLC) with aqueous-organic (methanol-water) and micellar-organic (sodium dodecyl sulphate (SDS)-pentanol) mobile phases of varying composition, and their octanol-water partition coefficients expressed as log P o/w (ranging between 2.02 for pheniramine and 4.92 for cyproheptadine), was examined. For this study, the retention of the drugs was measured in six mobile phases of methanol-water, and…
Complexes of tetra(parasulphonatephenyl)porphyrinato ferrate(III), FeTPPs, with 1,10 phenanthroline and 2,2′ bipyridine ligands
1985
Abstract Iron(III) porphyrin, FeTPPS, gives high-spin 1:1 monomeric complexes with the ligands 1,10 phenanthroline, 2,9 dimethylphenanthroline and 2,2 bipyridine in aqueous solution. Absorption spectrum of the complexes is very different to the one of the monomer metalloporphyrin, but nearly identical to the visible spectrum of the μ-oxo dimer Fe2(TPPS)2O. A spectrophotometric study of the formation equilibria yields the following values of the stability constants: Me2phen 4.3 × 104, phen 1.1 × 104, bipy 2.0 × 102 (25 °C, 0.1 M NaNO3). Analysis of the experimental data strongly suggest that the ligands are hydrogen bonded to one coordinated water molecule (TPPS)FeOH2 → (LL). Although the …
Effect of Large Changes in Temperature and Pressure on the Thermodynamic Properties of Micellization and on the Distribution Constant of a Polar Solu…
1996
Density measurements of pentanol (PentOH)−dodecyltrimethylammonium bromide (DTAB)−water mixtures as functions of both alcohol and surfactant (mS) concentrations were carried out at 0.1 MPa from 45 to 75 °C and at 19 MPa from 25 to 130 °C. The standard (infinite dilution) partial molar volumes and expansibilities of DTAB in water and the corresponding properties in the micellar phase were calculated from the experimental data. As far as PentOH in DTAB micellar solutions is concerned, with the exception of the standard partial molar volume (V°R) data at 130 °C and 19 MPa, all the V°R vs mS trends are monotonic curves with mS. The data of V°R as a function of mS were treated by means of an equ…
Influence of Phase Modifiers on the Degradation of Tri-n-octylamine/dodecane Extracting Mixture by an Acidic Solution of Vanadium (V)
2012
The kinetics of degradation of a mixture of tri-n-octylamine (extractant) and various alcoholic phase modifiers in n-dodecane in contact with acidic aqueous sulfate solutions containing vanadium (V) has been investigated. The nature of the modifier influences the kinetics of degradation and an improvement of the resistance against the chemical degradation is obtained when secondary alcohol (2-nonanol) or tertiary alcohols such as 9-octyl-9-heptadecanol are used as phase modifiers instead of 1-tridecanol. For instance, the kinetic constant of degradation is divided by one half when 9-octyl-9-heptadecanol is used as phase modifier instead of 1-tridecanol. On the contrary, the alcohols contain…
Protonation thermodynamics of 2,2'-bipyridyl in aqueous solution. Salt effects and weak complex formation
1993
Abstract Protonation constants of 2,2'-bipyridyl (bipy) have been determined potentiometrically, using (H + )-glass electrode, in different aqueous media (alkali and alkaline earth chlorides, tetramethylammonium chloride and tetramethylammonium iodide) at different temperatures and ionic strengths. The differences in log K H values are explained using a complex formation model. Formation thermodynamic parameters are given.
Thermodynamic parameters for the formation of glycine complexes with magnesium(II), calcium(II), lead(II), manganese(II), cobalt(II), nickel(II), zin…
1995
Abstract Protonation constants and Mg 2+ , Ca 2+ , Pb 2+ , Mn 2+ -, Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ and Cd 2+ glycine complex formation constants have been determined in different aqueous media at different temperatures. Salt effects are explained by a complex formation model which takes into account the formation of weak species. From the temperature dependence of the formation constants, thermodynamic parameters ΔH θ (and in some cases ΔC θ p ) have been obtained. A rigorous analysis of literature data, together with experimental findings, allows recommended formation parameters, in the ranges 0 ≤ I e ≤ 1 mol l −1 ( I e is the effective ionic strength) and 5°C ≤ T ≤ 45°C, to be obt…
Physicochemical Interactions Between Aroma Compounds and Milk Proteins: Effect of Water and Protein Modification
1998
The physicochemical interactions between aroma compounds and sodium caseinate were studied by complementary techniques involving the protein in aqueous solution at 25 or 75 g/L (exponential dilution and equilibrium dialysis) or in a solid state (sorption and infrared spectroscopy). No retention of acetone, ethyl acetate, and 2-propanol in aqueous solutions was found by exponential dilution and equilibrium dialysis. Diacetyl and benzaldehyde interacted with sodium caseinate through strong and weak bonds, as found by equilibrium dialysis. The results obtained by sorption differ from those obtained in aqueous solutions. The compounds that sorbed best to sodium caseinate were acetone and ethyl …
A thermodynamic study to evidence the alpha,omega-dichloroalkane/ block copolymer mixed aggregates formation: effect of the copolymer architecture.
2006
Abstract The thermodynamics of α , ω -dichloroalkanes in aqueous solutions of (ethylene oxide)11(propylene oxide)16(ethylene oxide)11 (L35) and (propylene oxide)8(ethylene oxide)23(propylene oxide)8 (10R5) was determined at 298 and 305 K. Modeling the experimental data allowed to calculate the standard free energy ( Δ G D o / w ) and the volume ( Δ V D / w ) for the additive–copolymer mixed aggregates formation per additive molecule. Δ G D o / w for Cl2CH2 and Cl2(CH2)2 evidenced that the process is controlled by the forces exercising between the chlorine atoms and the OH groups of the copolymer micelles protruded into the aqueous phase. Cl2(CH2)3 experiences both the hydrophilic and hydrop…