Complexation du cuivre(II) par les phénylsérines thréo et érythro: étude thermodynamique

1985 ◽  
Vol 63 (1) ◽  
pp. 46-51 ◽  
Author(s):  
Patrick Sharrock
Keyword(s):  
Aqueous Solution ◽  
Thermodynamic Parameters ◽  
Formation Constants ◽  
Side Chain ◽  
Potentiometric Measurements

Conductimetric and potentiometric measurements in aqueous solution as a function of temperature show that cupric ions promote the deprotonation of the hydroxy side chain of threo and erythro β-phenylserines. The threo ligand yields at 298 K the formation constants: Cu(L), K1 = 7.99; Cu(L)2, K2 = 6.71; Cu(L2H−1), K3 = −9.51; Cu(L2H−2), K4 = −10.83. The erythro isomer yields the corresponding constants: K1 = 7.70, K2 = 6.70, K3 = −9.82, and K4 = −11.20. Thermodynamic parameters for the first two complexation steps are −ΔH = 21.3 and 44.7 kJ mol−1; ΔS = 82 and 132 J K−1 mol−1, respectively, for the threo form and −ΔH = 20.7 and 44.1, ΔS = 79 and 129 for the erythro form. Deprotonation of the complexes corresponds to an additional enthalpy of −21 kJ mol−1. These results and the structures of the complexes are discussed.

scholarly journals Interaction of Ampicillin and Amoxicillin with Mn2+: A Speciation Study in Aqueous Solution

Molecules ◽  
2020 ◽  
Vol 25 (14) ◽  
pp. 3110
Author(s):  
Claudia Foti ◽  
Ottavia Giuffrè
Keyword(s):  
Aqueous Solution ◽  
Stability Constants ◽  
Metal Ion ◽  
Formation Constants ◽  
Enthalpy Change ◽  
Ligand Concentration ◽  
Empirical Parameter ◽  
Speciation Study ◽  
Potentiometric Measurements ◽  
The Stability

A potentiometric and UV spectrophotometric investigation on Mn2+-ampicillin and Mn2+-amoxicillin systems in NaCl aqueous solution is reported. The potentiometric measurements were carried out under different conditions of temperature (15 ≤ t/°C ≤ 37). The obtained speciation pattern includes two species for both the investigated systems. More in detail, for system containing ampicillin MLH and ML species, for that containing amoxicillin, MLH2 and MLH ones. The spectrophotometric findings have fully confirmed the results obtained by potentiometry for both the systems, in terms of speciation models as well as the stability constants of the formed species. Enthalpy change values were calculated via the dependence of formation constants of the species on temperature. The sequestering ability of ampicillin and amoxicillin towards Mn2+ was also evaluated under different conditions of pH and temperature via pL0.5 empirical parameter (i.e., cologarithm of the ligand concentration required to sequester 50% of the metal ion present in traces).

Polyether carboxylic acids incorporating a benzodioxinic subunit: synthesis and complexing ability of sodium and potassium

1992 ◽  
Vol 70 (3) ◽  
pp. 828-835 ◽  
Author(s):  
Pascal Bosseray ◽  
Gérard Coudert ◽  
Gérald Guillaumet ◽  
Georges Jeminet ◽  
Madeleine Tissier ◽  
...  
Keyword(s):  
Carboxylic Acids ◽  
Formation Constants ◽  
Side Chain ◽  
Complexing Ability ◽  
Potentiometric Measurements ◽  
Sodium And Potassium

We report here the synthesis of new polyoxygenated macrocyclic derivatives with a benzodioxinic subunit and a carboxylic side chain (2, 3), along with some of their corresponding acyclic polyethers (1). Formation constants of sodium and potassium complexes with both the acid and anion forms of these compounds were obtained from potentiometric measurements. The enhancement of both complexing ability and selectivity afforded by the presence of a carboxylic side chain is discussed. Keywords: polyether carboxylic acids, macrocycles, benzo-1,4-dioxin, sodium and potassium complexes, solvent methanol.

Fluorescence of the Complexes of 2-Methylnaphthoate and 2-Hydroxypropyl-α-, -β-, and -γ-Cyclodextrins in Aqueous Solution

2002 ◽  
Vol 56 (12) ◽  
pp. 1579-1587 ◽  
Author(s):  
Antonio Di Marino ◽  
Franscisco Mendicuti
Keyword(s):  
Aqueous Solution ◽  
Fluorescence Anisotropy ◽  
Intensity Ratio ◽  
Driving Forces ◽  
Emission Spectra ◽  
Formation Constants ◽  
Dielectric Constants ◽  
Additional Information ◽  
Fluorescence Techniques ◽  
Naturally Occurring

Fluorescence techniques were employed to study the inclusion complexes of 2-methylnaphthoate (MN) with 2-hydroxypropyl-α-cyclodextrin (αHPCD), 2-hydroxypropyl-β-cyclodextrin (βHPCD), and 2-hydroxypropyl-γ-cyclodextrin (γHPCD). Emission spectra of MN show two vibronic bands whose intensity ratio R is very sensitive to the polarity of the medium. The stoichiometry and formation constants of these complexes were investigated by obtaining R as a function of the cyclodextrin (CD) concentration. Results showed identical stoichiometry (1/1) for the three MN/αHPCD, MN/β-HPCD, and MN/γHPCD complexes. Formation constants at 25 °C were 780 ± 15, 2700 ± 130, and 165 ± 10 M−1, respectively. ΔH0 and ΔS0 were obtained from linear van't Hoff plots. Results reveal that the complexation of MN with αHPCD is enthalpy driven. With βHPCD, both the entropy and enthalpy terms favor the process, whereas the formation of the complex with γHPCD is entropically governed. The extrapolation of R at infinite CD concentration allows us to estimate the effective dielectric constants of the inner CD cavities, which are around 50, but which differ from their counterparts, the naturally occurring α-, β-, and γ-CDs. Fluorescence anisotropy, quencher lifetimes, and average lifetimes can also give additional information about the structure and driving forces accompanying the formation of such complexes.

Adsorption of Ni (II) from Aqueous Solution Based on Porous Magnetic/Chitosan Resin

2014 ◽  
Vol 936 ◽  
pp. 829-833
Author(s):  
Hai Song ◽  
Xing Hai Yu ◽  
Xiao Qin Zhang ◽  
Gui Fang Yan ◽  
Yuan Zhi Zhen
Keyword(s):  
Aqueous Solution ◽  
Aqueous Medium ◽  
Thermodynamic Parameters ◽  
Adsorption Process ◽  
Low Cost ◽  
Second Order ◽  
Magnetic Chitosan ◽  
Spontaneous Process ◽  
Chitosan Resin ◽  
Kinetics And Thermodynamic

The purpose of this work is to prepare a low-cost biosorbent,Porous Magnetic/Chitosan Resin(MCR), and determine the ability of this biosorbent to removing Ni (II) ion from aqueous medium. Both kinetics and thermodynamic parameters of the adsorption process were also estimated. The thermodynamic parameters indicated an exothermic spontaneous process and the kinetics followed the second-order adsorption process.

Thermochromism of Metal Exchange Reaction between Zinc(II) and Mercury(II) Porphyrins

1995 ◽  
Vol 50 (4) ◽  
pp. 545-550 ◽  
Author(s):  
Masaaki Tabata ◽  
Masahiro Ide ◽  
Kentaro Kaneko
Keyword(s):  
Aqueous Solution ◽  
Exchange Reaction ◽  
Thermodynamic Parameters ◽  
Distribution Curve ◽  
Equilibrium Constants ◽  
Metal Exchange ◽  
Free Base ◽  
Temperature Range ◽  
Base Form ◽  
Metal Exchange Reaction

Thermochromism was observed for an aqueous solution containing zinc(II) and mercury( II) cations and N-p-nitrobenzyl-5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin anion (NO2Bz(Htpps)4-) in the temperature range 10 to 70 °C. The equilibrium constants and the thermodynamic parameters of Zn(NO2Bztpps)3- and Hg(NO2Bztpps)3- have been determined spectrophotometrically to elucidate the thermochromism at 10, 15, 20, 25 and 30 °C in 0.1 mol dm-3 NaNO3. The protonation and metalation constants of NO2Bz(Htpps)4- are defined as K2 = [H2P][H+]-1[HP]-1, K3 = [H3P][H+]-1[H2P]-1 and KMP = [M P][H+][M2+]-1[HP]-1, where HP and MP denote the free base form of the prophyrin and the metalloporphyrins of zinc(II) and mercury(II), respectively. Charges of the prophyrin and metalloporphyrins are omitted for simplicity. The following values were found: logK2 = 7.75 ±0.02 (25 °C), ΔH°/kJmol-1 = -21.2±0.5 and ΔS°/Jmol-1K-1 = 77±1, logK3 = 2.55±0.02 (25 °C), ΔH°/kJmol-1 = -25±0.8 and ΔS°/Jmol-1K-1 = -35±3 and log KZnP = 0.63±0.03 (25 °C), ΔH°/kJmol-1 = 31.0±0.8 and ΔS°/Jmol-1K-1 = 116±3, logKHgP = 6.22±0.03 (25 °C), ΔH°/kJmol-1 = 4.5±0.7 and ΔS°/Jmol-1K-1 = 134±2. The distribution curve calculated from the thermodynamic parameters sufficiently agrees with the observed metal exchange reaction between the metalloporphyrins.

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