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Equilibrium Processes (equilibrium + process)
Selected AbstractsPeculiar kinetics of the complex formation in the iron(III),sulfate systemINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 3 2008Balázs Kormányos The results of comprehensive equilibrium and kinetic studies of the iron(III),sulfate system in aqueous solutions at I = 1.0 M (NaClO4), in the concentration ranges of T = 0.15,0.3 mM, and at pH 0.7,2.5 are presented. The iron(III),containing species detected are FeOH2+ (=FeH,1), (FeOH) (=Fe2H,2), FeSO, and Fe(SO4) with formation constants of log , = ,2.84, log , = ,2.88, log , = 2.32, and log , = 3.83. The formation rate constants of the stepwise formation of the sulfate complexes are k1a = 4.4 × 103 M,1 s,1 for the step and k2 = 1.1 × 103 M,1 s,1 for the step. The mono-sulfate complex is also formed in the reaction with the k1b = 2.7 × 105 M,1 s,1 rate constant. The most surprising result is, however, that the 2 FeSO, Fe3+ + Fe(SO4) equilibrium is established well before the system as a whole reaches its equilibrium state, and the main path of the formation of Fe(SO4) is the above fast (on the stopped flow scale) equilibrium process. The use and advantages of our recently elaborated programs for the evaluation of equilibrium and kinetic experiments are briefly outlined. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 114,124, 2008 [source] Thin semitransparent gels containing phenylboronic acid: porosity, optical response and permeability for sugarsJOURNAL OF MOLECULAR RECOGNITION, Issue 2 2008Alexander E. Ivanov Abstract Radical copolymerization of acrylamide (Am) (90,mol%) with N -acryloyl- m -aminophenylboronic acid (NAAPBA) (10,mol%) carried out on the surface of glass slides in aqueous solution and in the absence of chemical cross-linkers, resulted in the formation of thin semitransparent gels. The phenylboronic acid (PBA) ligand density was ca. 160,µmol/ml gel. The gels exhibited a macroporous structure and displayed optical response to sucrose, lactose, glucose and fructose in 50,mM sodium phosphate buffer, in the pH range from 6.5 to 7.5. The response was fairly reversible and linearly depended on glucose concentration in the wide concentration range from 1 to 60,mM at pH 7.3. The character of response was explained by the balance of two competing equilibrium processes: binding of glucose to phenylboronate anions and binary hydrophobic interactions of neutral PBA groups. The apparent diffusion coefficient of glucose in the gels was ca. 2.5,×,10,7,cm2/s. A freshly prepared gel can be used daily for at least 1 month without changes in sensitivity. Autoclaving (121°C, 1.2 bar, 10,min) allows for the gels sterilization, which is important for their use as glucose sensors in fermentation processes. Copyright © 2008 John Wiley & Sons, Ltd. [source] Molecular and macroscopic modeling of phase separationAICHE JOURNAL, Issue 10 2000Fernando A. Escobedo Recently proposed pseudoensemble Monte Carlo methods are extended in this work to map out diverse phase diagrams (projections of the phase-coexistence hypersurface) of multicomponent mixtures required to characterize fluid-phase equilibrium phenomena and to design separation processes. Within the pseudoensemble framework, the macroscopic models of different equilibrium processes can be readily integrated to the mathematical constraints that specify the thermodynamic state of the system. The proposed Monte Carlo methods allow, for example, the simulation of isopleths and cloud-point lines to compare experimental to simulation data and to test molecular force fields. Applications of this approach include the study of retrograde phenomena in a model natural-gas mixture through simulation of dewlines and coexistence lines at constant vaporization fraction. As demonstrated, pseudoensemble simulations can also be used to generate the thermodynamic data necessary to solve problems encountered in continuous and discontinuous distillation processes. [source] Intra-articular depot formulation principles: Role in the management of postoperative pain and arthritic disordersJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 11 2008Claus Larsen Abstract The joint cavity constitutes a discrete anatomical compartment that allows for local drug action after intra-articular injection. Drug delivery systems providing local prolonged drug action are warranted in the management of postoperative pain and not least arthritic disorders such as osteoarthritis. The present review surveys various themes related to the accomplishment of the correct timing of the events leading to optimal drug action in the joint space over a desired time period. This includes a brief account on (patho)physiological conditions and novel potential drug targets (and their location within the synovial space). Particular emphasis is paid to (i) the potential feasibility of various depot formulation principles for the intra-articular route of administration including their manufacture, drug release characteristics and in vivo fate, and (ii) how release, mass transfer and equilibrium processes may affect the intra-articular residence time and concentration of the active species at the ultimate receptor site. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:4622,4654, 2008 [source] Theoretical features of macrocyclization equilibria and their application on transacetalation based dynamic librariesJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 9 2010Stefano Di Stefano Abstract The theoretical treatment of macrocyclization reactions under thermodynamic control is overviewed in the light of recent growing interest toward Dynamic Combinatorial Chemistry (DCC). The rules governing the equilibrium processes in Dynamic Library (DL) under conditions of perfect mass balance are illustrated. Data related to transacetalation reactions of cyclophane formaldehyde acetals are thoroughly discussed as remarkable examples of systems where experiments and theory make a good match. Copyright © 2010 John Wiley & Sons, Ltd. [source] | ||||||||||