Solution speciation in the aqueous Na(I)–EDTA and K(I)–EDTA systems

1993 ◽  
Vol 71 (5) ◽  
pp. 763-768 ◽  
Author(s):  
Min Chen ◽  
R. Stephen Reid
Keyword(s):  
Potentiometric Titration ◽  
Ethylenediaminetetraacetic Acid ◽  
Dissociation Constants ◽  
Equilibrium Constants ◽  
Acid Dissociation ◽  
Equilibrium Models ◽  
Acid Dissociation Constants ◽  
Aqueous Sodium ◽  
Ph Values ◽  
Solution Speciation

Speciation in the aqueous sodium(I) – ethylenediaminetetraacetic acid and potassium(I) – ethylenediaminetetraacetic acid equilibrium systems was investigated by automated gravimetric potentiometric titration. It was found that in both cases, particularly below neutral pH values, speciation includes a previously uncharacterized diprotonated complex. All formation and acid dissociation constants were measured for the full systems. The validity of previous literature equilibrium constants, which are based on incomplete equilibrium models, is discussed.

Decomposition of some cyclic dithiocarbamates

1970 ◽  
Vol 48 (14) ◽  
pp. 2204-2209 ◽  
Author(s):  
Ronald R. Vandebeek ◽  
Serge J. Joris ◽  
Keijo I. Aspila ◽  
Chuni L. Chakrabarti
Keyword(s):  
Dielectric Constant ◽  
Dissociation Constants ◽  
Acid Dissociation ◽  
Acid Molecule ◽  
Decomposition Rates ◽  
Acid Dissociation Constants ◽  
Ring Strain ◽  
Relative Stabilities ◽  
Ph Values ◽  
The Stability

The stability of some cyclic N,N-disubstituted dithiocarbamates has been studied by the analysis of the decomposition rates at different pH values. It is concluded that the most important factors which determine the relative stabilities of three cyclic dithiocarbamates (DTC) are the solvation of the DTC acid molecule and the ring strain associated with the substituents. This has been proven by a study of (a) the decomposition rates as a function of the dielectric constant of the medium, (b) order of the stability, and (c) activation energy.The molar absorptivities and the apparent acid dissociation constants have been determined for pyrrolidine-, piperidine-, and hexamethylene-dithiocarbamates.

Equilibrium studies on lithium(I) transfer into ionic liquid with a water-soluble octabromoporphyrin (H2(OBTMPyP)4+) from aqueous phase

2009 ◽  
Vol 13 (08n09) ◽  
pp. 849-853 ◽  
Author(s):  
Takuya Shimomura ◽  
Masaaki Tabata ◽  
Jun Nishimoto
Keyword(s):  
Aqueous Solution ◽  
Ionic Liquid ◽  
Ion Exchange ◽  
Dissociation Constants ◽  
Equilibrium Constants ◽  
Water Soluble ◽  
Acid Dissociation ◽  
Acid Dissociation Constants ◽  
Equilibrium Studies ◽  
Counter Ions

A water-soluble octabromoporphyrin 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin (H2(OBTMPyP)4+), H2P4+) and its lithium complex, Li(OBTMPyP)3+ , (LiP3+) , transferred quantitatively to an ionic liquid (IL), 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM+PF6-) with no addition of other counter ions. The acid-dissociation constants of H2(OBTMPyP)4+ between aqueous and BMIM+PF6- phases were determined spectrophotometrically and found to be 10-7.67 and 10-11.33 at I = 0.1 for K a1,IL = [H+]aq[HP3+]IL/[H2P4+]IL and K a2,IL = [H+]aq[P2+]IL/[HP3+]IL , respectively. Since the acid-dissociation constants involve the partition of H2(OBTMPyP)4+ between aqueous and IL phases, the determined values are ten times as low as those observed in aqueous solution. The transfer equilibrium constants of LiP3+ and NaP3+ to IL defined by K MP,IL = [MP3+]IL/[M+]aq[P2+]IL (M = Li+ or Na+) were found to be 104.83 and 101.31 for K LiP,IL and KNaP,IL , respectively. LiP3+ transferred selectively in the presence of Na+ (K LiP,IL /K NaP,IL = 103.52) to IL phase through an ion-exchange mechanism between BMIM+PF6- and Li(OBTMPyP)3+ .

Article

1998 ◽  
Vol 76 (5) ◽  
pp. 576-582
Author(s):  
Patricia Gabriela Molina ◽  
María Alicia Zón ◽  
Héctor Fernández
Keyword(s):  
Dissociation Constants ◽  
Monomethyl Ether ◽  
Spectroscopic Studies ◽  
Acid Dissociation ◽  
Alternariol Monomethyl Ether ◽  
Acid Dissociation Constants ◽  
Ph Values ◽  
Acidic Constant ◽  
Acidic Constants ◽  
Good Agreement

The acid dissociation constants for alternariol monomethyl ether (AME), altertoxin-I (ATX-I), and alternariol (AOH), three of the Alternaria alternata genus mycotoxins, are estimated through conventional UV-VIS spectroscopic studies at different pH values. Experimental variations of absorbance as a function of pH at a given wavelength were fitted by using the exact equations that describe the systems studied. Good agreement between the experimental absorbance vs. pH plots and the curves generated by the fitting process was found. A comparison between the acidic constants for the first step of dissociation of these mycotoxins and the value for the acidic constant of phenol is discussed by assuming that phenolic structures are responsible for the acidity of these mycotoxins.Key words: mycotoxins, alternariol monomethyl ether, altertoxin-I, alternariol, acidic constants.

Equilibria in the halogenation of some organic substances in aqueous solution

1952 ◽  
Vol 210 (1102) ◽  
pp. 310-322 ◽  
Keyword(s):  
Gas Phase ◽  
Dissociation Constants ◽  
Equilibrium Constants ◽  
Mean Value ◽  
Acid Dissociation ◽  
Organic Substances ◽  
Kcal Mole ◽  
Acid Dissociation Constants ◽  
The Mean ◽  
Better Than

Measurements of redox potential have been used to obtain equilibrium constants for the reaction of iodine and bromine with aqueous solutions of ketones, esters and nitro-paraffins. Many of the iodination constants have an accuracy of a few per cent, but the bromination constants are not reliable to better than a power of ten. The iodination constants vary over 10 powers of ten, corresponding to considerable differences in the nature of the carbonhydrogen and carbon-iodine bonds involved. The data are used to derive the heat of the reaction R H + I-> R I + H in the gas phase, and the mean value obtained (46 kcal/mole) is consistent with earlier estimates. Approximate values are also derived for the equilibrium constants of the reaction R I->R - + I + in solution. For variations in R these are roughly parallel with the acid dissociation constants of the reaction R H->R - + H + .

Axial coordination reactions with nitrogenous bases and determination of equilibrium constants for zinc tetraarylporphyrins containing four β,β′-fused butano and benzo groups in nonaqueous media

2019 ◽  
Vol 23 (01n02) ◽  
pp. 196-205 ◽  
Author(s):  
Lina Ye ◽  
Yuanyuan Fang ◽  
Zhongping Ou ◽  
Liping Wang ◽  
Songlin Xue ◽  
...  
Keyword(s):  
Dissociation Constants ◽  
Equilibrium Constants ◽  
Acid Dissociation ◽  
Nonaqueous Media ◽  
Acid Dissociation Constants ◽  
Axial Coordination ◽  
Conjugate Acid ◽  
Nitrogenous Base ◽  
Spectral Titration

The axial coordination properties of six zinc tetraarylporphyrins with seven different nitrogenous bases were examined in CH2Cl2 for derivatives containing four [Formula: see text],[Formula: see text]-fused butano or benzo groups and the equilibrium constants (log[Formula: see text] determined using spectral titration methods. The examined compounds are represented as butano(YPh)4PorZn and benzo(YPh)4PorZn, where Por is the porphyrin dianion and Y is a CH3, H or Cl substituent on the para-position of each meso-phenyl ring of the macrocycle. The initial four-coordinate butano- and benzoporphyrins will axially bind one nitrogenous base to form five-coordinate derivatives in CH2Cl2 and this leads to a 4–22 nm red-shift of the Soret and Q bands. The log[Formula: see text] values range from 1.98 to 4.69 for butano(YPh)4PorZn and from 3.42 to 5.36 for benzo(YPh)4PorZn, with the exact value depending upon the meso and [Formula: see text]-substituents of the porphyrin and the conjugate acid dissociation constants (p[Formula: see text] of the nitrogenous base.

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