Acid dissociation constants and pH values for standard “bes” and “tricine” buffer solutions in 30, 40, and 50 mass% dimethyl sulfoxide/water between 25 and −25 °C

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.

Download Full-text

Re-examination of the Kirkwood–Westheimer theory of electrostatic effects. III. Dissociation constants of cis-3- and trans-4-substituted cyclohexanecarboxylic acids in water–dimethyl sulfoxide mixtures

Canadian Journal of Chemistry ◽

10.1139/v78-190 ◽

1978 ◽

Vol 56 (8) ◽

pp. 1130-1133 ◽

Cited By ~ 3

Author(s):

Jitka Kirchnerova ◽

Patrick G. Farrell ◽

John T. Edward ◽

Jean-Claude Halle ◽

Robert Schaal

Keyword(s):

Dimethyl Sulfoxide ◽

Dissociation Constant ◽

Dissociation Constants ◽

Solvent Composition ◽

Potentiometric Method ◽

Acid Dissociation ◽

Electrostatic Effects ◽

Acid Dissociation Constants ◽

Cyclohexanecarboxylic Acid

Acid dissociation constants of two cis-3- and of four trans-4-substituted cyclohexanecarboxylic acids in water – dimethyl sulfoxide mixtures of varying composition were determined by a potentiometric method. Results have been analyzed according to the model of Kirkwood and Westheimer, and shown to differ from calculated values because of certain oversimplifications built into the model. Dissociation constant differences between cyclohexanecarboxylic acid and the compounds studied vary only slightly with changing solvent composition.

Download Full-text

Article

Canadian Journal of Chemistry ◽

10.1139/v98-061 ◽

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.

Download Full-text

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

Canadian Journal of Chemistry ◽

10.1139/v93-100 ◽

1993 ◽

Vol 71 (5) ◽

pp. 763-768 ◽

Cited By ~ 5

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.

Download Full-text