Acid-base strengths in m-cresol

For various acids and bases dissociation constants were determined conductimetrically in m-cresol. A glass electrode was calibrated by means of some compounds with dissociation constants known from conductivity measurements. Potentiometric titrations with this calibrated glass electrode gave dissociation constants of some other acids and bases in m-cresol. The value 2·10−19 was found for the self-dissociation constant of m-cresol. From the difference pKa (cresol) - pKa (pyridine) for those compounds having acid or base strengths which are not levelled either in pyridine or m-cresol, it was found that the solvent m-cresol has a basicity about 8 pK units less than that of pyridine

Dissociation constants and thermodynamic properties of amino acids used in CO2 absorption from (293 to 353) K

The second dissociation constants of the amino acids βalanine, taurine, sarcosine, 6-aminohexanoic acid, DL-methionine, glycine, L-phenylalanine, and L-proline and the third dissociation constants of L-glutamic acid and L-aspartic acid have been determined from electromotive force measurements at temperatures from (293 to 353) K. Experimental results are reported and compared to literature values. Values of the standard state thermodynamic properties are derived from the experimental results and compared to the values of commercially available amines used as absorbents for CO 2 capture.

Dissociation Constants of Tetraphosphoric Acid

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Calculation of acid dissociation constants

A computational method has been developed for the determination of dissociation constants of acids (and bases). The method is applicable to mono or polybasic acids and, in certain cases, to mixtures of acids. A least-squares treatment is employed, and no simplifying assumptions are made in any of the equations or factors involved. All the available data are utilized, and provision is made for including or calculating activity coefficients. Utilization of the method requires a medium to large size digital computer

Aqueous Equilibria: Acids, Bases, and Solubility. A General Chemistry Laboratory Experiment

We refer to two major types of general chemistry freshman laboratory experiments: discovery and cookbook. The typical Freshman enrolled in general chemistry has the skills to perform an experiment that is somewhere between cookbook and discovery, and we have developed a laboratory experiment that is midway between these extremes. This experiment aids the student\u27s understanding of the concept of aqueous equilibria. In this experiment, students are asked to prepare and measure the pH of a variety of acidic and basic solutions. Students are also asked to calculate pH values from literature dissociation constants and dissociation constants from their experimental pH values. This experiment demonstrates the relationships between dissociation constants, percent ionization, pH and strength of acids and bases, as well as molar solubility and the solubility product constant, Ksp. A Mathcad-based prelaboratory activity provides a review of the concepts and engages students in what-if explorations

HYDROGEN BONDING IN betabeta-NITRO ALCOHOLS. III. PYRIDINE COMPLEXES

BETA -Nitro alcohols form stable 1:1 complexes with pyridine, examples of which were prepared. In solvents such as dichloromethane and carbon tetrachloride the complexes partially dissociate into their components. The dissociation constants for the equilibria were determined by infrared methods and may be used as a measure of the strength of the complex hydrogen bond. The dissociation constants decrease with increasing number of BETA -nitro groups. Some reactions of the pyridine complexes are described. (auth

Fast fluorescence dynamics in non-ratiometric calcium indicators

A fluorescence decay of high-affinity non-ratiometric Ca2+ indicator Oregon Green BAPTA-1 (OGB-1) is analyzed with unprecedented temporal resolution in the two-photon excitation regime. A triple exponential decay is shown to best fit the fluorescence dynamics of OGB-1. We provide a new model for accurate measurements of the free Ca2+ concentration and dissociation constants of non-ratiometric calcium indicators.Comment: 3 pages, 2 figures, figures revised, added chi-square goodness of fi

Liesegang patterns: Effect of dissociation of the invading electrolyte

The effect of dissociation of the invading electrolyte on the formation of Liesegang bands is investigated. We find, using organic compounds with known dissociation constants, that the spacing coefficient, 1+p, that characterizes the position of the n-th band as x_n ~ (1+p)^n, decreases with increasing dissociation constant, K_d. Theoretical arguments are developed to explain these experimental findings and to calculate explicitly the K_d dependence of 1+p.Comment: RevTex, 8 pages, 3 eps figure