Search results for "aqueous solution"
showing 10 items of 1610 documents
Polymer−Surfactant Interactions. A Quantitative Approach to the Enthalpy of Transfer of Poly(Ethylene Glycol)s from Water to the Aqueous Sodium Perfl…
2000
The enthalpy of transfer (ΔHt) of nonionic polymers at a fixed concentration from water to aqueous substrate solutions as a function of the substrate concentration (fSmS) was determined. The substrates studied are sodium perfluorobutanoate to sodium perfluorooctanoate, and the polymers are poly(ethyleneglycol)s with molecular weights of 400 and 35 000. For the PEG 400-sodium perfluoroheptanoate−water systems, measurements were also performed at some polymer compositions. As a general feature, the enthalpy of transfer steeply changes with fSmS, reaching a maximum beyond which it decreases, tending to level off. A qualitative analysis of the enthalpy data assigned the steep increase of ΔHt to…
Wirkung der Insektizide Allethrin, Lindan und Jacutin-Fogetten-Sublimat auf den photosynthetischen Elektronentransport
1977
Summary During our studies of Hill-reactions of isolated chloroplasts we observed an inhibition of electron transport after an application of the smoke of «Jacutine-Fogetten» in the plant growth chamber. Therefore we tested the influence of the insecticides Lindane (Gammexan), the sublimate formed by the fumigation of «Jacutin Fogetten», and of Allethrin on the photosynthetic electron transport reactions of PS II and PS I. 39 μ M Lindane inhibits the basal, coupled and uncoupled electron transport to ferricyanide of broken chloroplasts isolated from leaves of Pisum sativum up to 35%. A higher inhibitory effect with higher concentrations is limited by the low water solubility of Lindane. On …
Enzymatische hydrolyse hydrophiler ester durch lipasen - eine milde carboxydeblockierung von peptiden und glycopeptiden
1993
Abstract The markedly hydrophilic 2-(N-morpholino)ethyl (MoEt) esters of protected peptides and glycopeptides are selectively and efficiently cleaved by lipases in water/acetone (10:1) at pH 7.
Speciation of Low Molecular Weight Carboxylic Ligands in Natural Fluids: Protonation Constants and Association with Major Components of Seawater of O…
1999
Abstract The interaction of oxydiacetate and citrate with the major components of seawater has been studied potentiometrically, at 25°C, in an artificial seawater (containing Na+, K+, Ca2+, Mg2+, Cl− and SO42−) at different salinities (5–45‰). Apparent protonation constants were calculated, from potentiometric data, and estimated, using an appropriate complex formation model. Formation constants of complexes formed by oxydiacetate and citrate and the cation of seawater (the inorganic content of seawater being considered as a single 1 : 1 salt) were determined. The single salt approximation for the major inorganic components of seawater, which is a good tool in estimating the mean strength o…
Interaction of Alkyltin(IV) Compounds with Ligands of Interest in the Speciation of Natural fluids: Complexes of (CH3)2Sn2+ with Carboxylates
1997
Complex formation by (CH3)2Sn 2+ with acetate (ac), malonate (mal), 1,2,3-propanetricarboxylate (tricarballylate, tca) and 1,2,3,4-butanetetracarboxylate (btc) ligands in aqueous solution is reported. The study has been performed by potentiometry ([H + ]‐glass electrode) at T = 25 °C, and in the 0 < I < 1 mol dm 2 3 ionic strength range. In order to evaluate the salt effects on the formation constants of the complex species, and to contribute to the definition of the chemical speciation of diorganotin(IV) compounds in natural waters where carboxylic ligands are naturally present, interactions of NaCl (which is the major component of all natural fluids), with the components of the systems un…
Speciation of organotin compounds in NaCl aqueous solution: interaction of mono-, di- and tri-organotin(IV) cations with nucleotide 5′ monophosphates
2004
Formation constants for complex species of mono-, di- and tri-alkyltin(IV) cations with some nucleotide 5'-monophosphates (AMP, UMP, IMP and GMP) are reported, at T=25°C and at I = 0.16 mol 1 -1 (NaCI). The investigation was performed in the light of speciation of organometallic compounds in natural fluids in the presence of nucleotides whose biological importance is well recognized. The simple and mixed hydrolytic complex species formed in all the systems investigated in the pH range 3-9 are (L = nucleotide; M = organotin cation R x Sn (4-x)+ , with x = 1 to 3): ML + , ML(OH)° and ML(OH) 2 - for the system CH 3 Sn 3+ -L (L = AMP, IMP, UMP); ML 0 and ML(OH)-for the system (C 2 H 5 ) 2 Sn 2+…
Complexation of phosphine ligands with peracetylated β-cyclodextrin in supercritical carbon dioxide: Effect of temperature and cosolvent on the equil…
2009
Abstract The interaction between peracetylated-β-cyclodextrin and tert-butyl and adamantyl functionalized triphenylphosphine derivatives was studied in supercritical carbon dioxide (scCO 2 ) based solvent media by UV–vis spectroscopy. The equilibrium constant for a 1:1 complexation reaction was obtained from titration spectra both in pure carbon dioxide and in the presence of methanol as a cosolvent in the temperature range 308–323 K to estimate the internal energy and entropy of the inclusion equilibrium. The values of the equilibrium constants were found significantly smaller than those obtained in aqueous solution with analogous phosphines and substantially independent of the nature of t…
Studies of the ternary systems humic substances – kaolinite – Pu(III) and Pu(IV)
2008
AbstractThe behaviour of plutonium with respect to its migration in the aquifer has been studied under conditions close to nature. Most relevant under these conditions are Pu(III) and Pu(IV) in contact with humic substances (HS) and minerals. As a model for the host rock, kaolinite (KGa-1b) was chosen. The complexation of Pu(III) and Pu(IV) with Aldrich humic acid (AHA) in aqueous solution at ionic strength 0.1 M was investigated by the ultrafiltration method. The sorption of Pu(III) and Am(III) onto kaolinite (K) as a function of pH and metal-ion concentration was studied under aerobic and anaerobic conditions. The pH edge was found at pH∼5.5 independent of the metal-ion concentration and …
ChemInform Abstract: Review: Solution Equilibria of Ternary Complexes Formed from Copper(II), Aliphatic Amines, and Bioligands
2014
This review provides a summary of the coordination chemistry of ligands in the ternary system: copper(II)–aliphatic amine–bioligand, where amine = ethylenediamine – En, diethylenetriamine – Dien, or N, N, N′, N″, N″-pentamethyldiethylenetriamine – Me5dien, and bioligand = selected amino acid, aminohydroxamic acid, or aminophosphonic acid, in aqueous solution. We would like to show the specific interactions of copper(II) in ternary systems in the context of complex equilibria chemistry.
Equilibria involved in the diorganotin(IV) and triorganotin(IV) phosphomycin interaction in aqueous solution
2007
Four new diorganotin(IV), (R = Me, Bu), and triorganotin(IV), (R = Me, Ph), derivatives of the phosphomycin disodium salt antibiotic[(1R,2S)-1,2-epoxypropylphosphonate]Na2 have been synthesized and their solid state configuration studied by X-ray crystallography, FT-IR, Mossbauer, UV–Vis spectroscopies. The X-ray diffraction investigation, performed on the bis[trimethyltin(IV)]- phosphomycin, showed that the coordination geometry at all the Sn atoms is trigonal bipyramidal. The structure of the complex forms an unusual polymeric zig-zag planar network. The FT-IR and the 119Sn Mo¨ssbauer studies supported the formation of trigonal bipyramidal (Tbp) molecular structures, both in the diorganot…