scholarly journals Analysis of acid-base properties of some p-substituted aromatic hydrazones in aqueous perchloric acid by spectrophotometric and semiempirical methods

2014 ◽  
Vol 33 (1) ◽  
pp. 85 ◽  
Author(s):  
Mirjana Stojan Jankulovska ◽  
Ilinka Spirevska
Keyword(s):  
Perchloric Acid ◽  
Dissociation Constants ◽  
Protonated Form ◽  
Heat Of Formation ◽  
Semiempirical Methods ◽  
Acid Base ◽  
Spectrophotometric Methods ◽  
Aqueous Perchloric Acid ◽  
The Stability ◽  
Base Properties

<p>The acid-base properties of some <em>p</em>-substituted aromatic hydrazones were examined in aqueous perchloric acid medim by spectrophotometric methods. The possible site where the proton may take place and the stability of the protonated form was discussed using the values of the total energy, binding energy, heat of formation and proton affinity calculated according to the semiempirical methods AM1 and PM3. Furthermore, the stability of the protonated forms, as well as, the stability of the isomers (<em>E</em> and <em>Z</em>) was discussed. Electronic absorption studies were utilized for determination of the dissociation constants of the protonated form (p<em>K</em><sub>BH</sub><sup>+</sup>), numerically and graphically, at different ionic strength (0.1, 0.25 and 0.5 mol/dm<sup>3</sup>), as well as, thermodynamic dissociation constants.  The influence of the solvent on the appearance of the recorded spectra was compensated by the use of the method of characteristic vector analysis (CVA).</p><p> </p>

Quantitative description of the changes in the acid-base properties of bromocresol green in the presence of submicelle and micelle concentrations of cationic tenside-Septonex

1983 ◽  
Vol 48 (5) ◽  
pp. 1290-1304 ◽  
Author(s):  
Josef Havel ◽  
Irena Burešová-jančářová ◽  
Vlastimil Kubáň
Keyword(s):  
Dissociation Constant ◽  
Equilibrium Constant ◽  
Dissociation Constants ◽  
Quantitative Description ◽  
Polymeric Micelle ◽  
Bromocresol Green ◽  
Acid Base ◽  
Experimental Conditions ◽  
Spectrophotometric Methods ◽  
Base Properties

The effect of cationic surface-active substances - tensides - on the acid-base and optical properties of anionic organic analytical reagents was studied by spectrophotometric methods on the example of bromocresol green with Septonex in the submicelle and micelle tenside concentration regions. The acid-base properties of bromocresol green under the given experimental conditions depend on the concentrations of the tenside and reagent and on the type and concentration of the inert electrolyte. Changes in the conditional dissociation constant of the reagent were quantitatively described by equations that were derived from the relationships for the dissociation constant of the acid-base transition of the reagent LH/L-, the equilibrium constant for formation of the stoichiometric ion-associates between the tenside T+ and the anionic acid-base form of the reagent L- or the anion of the inert electrolyte X- and the equilibrium constant for formation of the polymeric micelle aggregates (T+)n. The experimental values of the conditional dissociation constants for bromocresol green for various tenside or inert electrolyte concentrations are in good agreement with these theoretically derived relationships.

Acid-base properties of 1,3-diphenyl-5-(1H-tetrazol-2-yl)formazan and 1,3-diphenyl-5-(2H-1,2,4-triazol-3-yl)formazan

1982 ◽  
Vol 47 (11) ◽  
pp. 2882-2889
Author(s):  
Nadezhda Likhareva ◽  
Ladislav Šůcha ◽  
Miloslav Suchánek
Keyword(s):  
Computer Program ◽  
Dissociation Constants ◽  
Acid Base ◽  
New Compounds ◽  
Base Properties

Two new compounds from the formazan series, viz. 1,3-diphenyl-5-(1H-tetrazol-2-yl)formazan and 1,3-diphenyl-5-(2H-1,2,4-triazol-3-yl)formazan, were prepared, and the dissociation constants and molar absorptivities of all of their acid-base species were determined spectrophotometrically employing the SPEKTFOT computer program.

scholarly journals UV Spectrophotometric Determination of Thermodynamic Dissociation Constants of Some Aromatic Hydrazones in Acid Media

2019 ◽  
Vol 63 (4) ◽  
Author(s):  
Mirjana Jankulovska ◽  
Ilinka Spirevska ◽  
Vesna Dimova ◽  
Milena Jankulovska
Keyword(s):  
Proton Affinity ◽  
Dissociation Constants ◽  
Uv Spectroscopy ◽  
Sodium Perchlorate ◽  
Atomic Charge ◽  
Protonated Form ◽  
Uv Spectra ◽  
Semiempirical Methods ◽  
Acid Media ◽  
Protonation Site

The spectral behavior of some p-nitro-p-substituted benzoylhydrazones in the perchloric acid media was followed, applying the UV spectroscopy. The position of the absorption maximum in the spectra was defined in acidic media and the electronic transitions were discussed, as well (7<pH<1). The equilibrium between neutral and protonated form was investigated in the ethanol-water (V/V, 1:1) solutions. The observed changes in the UV spectra suggested that protonation process took place in one step. The pH region of protonation ranges between 1.4 and 2.9. Using the changes in the UV spectra which appear as a result of the protonation reaction the stoichiometric dissociation constants were determined numerically (pKBH+ = n·pH + logI) and graphically (intercept of the dependence of logI on pH). Thermodynamic dissociation constants were estimated as an intercept of dependence of pKBH+ on square root of the ionic strength. In order to achieve that, measurements were performed at different ionic strengths: 0.1, 0.25 and 0.5 mol/dm3, adjusted with sodium perchlorate. The obtained thermodynamic pKBH+ values ranged between 2.07 and 2.58. In order to predict proton transfer at a given pH, semiempirical methods AM1 and PM3 were applied. The influence of the substituents present in the p-position of the benzene ring on pKBH+ values of investigated hydrazones was discussed, too. Total energy, binding energy, enthalpy of formation, Gibbs energies of formation, atomic charge and proton affinity values were used to predict protonation site in hydrazone molecule. Furthermore, the stability and the proton affinity of the isomers (E and Z) in which hydrazones exist and their protonated forms were defined.

Acid–base behaviour of the ferricyanide ion in perchloric acid media. Spectrophotometric and kinetic study

1990 ◽  
Vol 68 (2) ◽  
pp. 228-235 ◽  
Author(s):  
Pedro L. Domingo ◽  
Begoña García ◽  
José M. Leal
Keyword(s):  
Kinetic Study ◽  
Perchloric Acid ◽  
Decomposition Reaction ◽  
Acid Base ◽  
Acid Media ◽  
Protonation Equilibria ◽  
Aqueous Perchloric Acid ◽  
Protonated Species ◽  
Heterolytic Dissociation ◽  
Homolytic Dissociation

A wide study was carried out of the acid–base behaviour of ferricyanide ions in aqueous perchloric acid media in the range 0.1–11.5 M. This study shows that protonation and decomposition of the ferricyanide ions occur simultaneously. The three successive protonation equilibria were found in the acidity ranges 0.1–4.0, 3.5–8.5, and 7.0–11.5 M HClO4, respectively. A kinetic study was also made of the decomposition reaction at 60 °C. The kinetic data are explained by considering a reaction mechanism involving homolytic and heterolytic dissociation steps. The homolytic and heterolytic rate constants corresponding to each of the four protonated species were determined, along with the acid–base protonation constants, pK1 = −6.25 ± 0.10; pK2 = −3.23 ± 0.03; and pK3 = −0.60 ± 0.02. Keywords: acid–base behaviour, protonated species, decomposition, homolytic dissociation, heterolytic dissociation.

scholarly journals Studies on the Stability of Amides. III. Hydrolysis of Amides in Aqueous Perchloric Acid Solution

1972 ◽  
Vol 20 (8) ◽  
pp. 1778-1784 ◽  
Author(s):  
TSUKINAKA YAMANA ◽  
YUZO MIZUKAMI ◽  
AKIRA TSUJI ◽  
MASAHIRO IKUTA
Keyword(s):  
Acid Solution ◽  
Perchloric Acid ◽  
Perchloric Acid Solution ◽  
Aqueous Perchloric Acid ◽  
The Stability ◽  
Hydrolysis Of

Synthesis and acid–base properties of a proton-bridged biaryl compound based on pyridylazulene

2015 ◽  
Vol 39 (12) ◽  
pp. 9079-9085 ◽  
Author(s):  
Kazuki Ninomiya ◽  
Yumi Harada ◽  
Tomoaki Kanetou ◽  
Yuma Suenaga ◽  
Toshihiro Murafuji ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Intramolecular Hydrogen Bond ◽  
Protonated Form ◽  
Acid Base ◽  
Intramolecular Hydrogen ◽  
Base Properties

We report the synthesis and acid–base properties of 1,1′-bi(2-pyridylazulene) and the crystal structure of its mono-protonated form in which pyridyl moieties are interacted by an intramolecular hydrogen bond.

Salicylhydroxamic acid and its iron(III) complexes

1987 ◽  
Vol 52 (3) ◽  
pp. 602-608 ◽  
Author(s):  
Vladimír Špringer ◽  
Magdaléna Horňáčková ◽  
Rolf Karlíček ◽  
Božena Kopecká
Keyword(s):  
Stability Constant ◽  
Dissociation Constants ◽  
Salicylhydroxamic Acid ◽  
Spectrophotometric Methods ◽  
The Stability

The dissociation constants of salicylhydroxamic acid (H2L), pKa1 = 6.73 and pKa2 = 9.15 (20 °C, I = 1.0 (NaClO4)), and the stability constant of the FeHL2+ complex, logβ = 9.09, were determined by the potentiometric and spectrophotometric methods. The low-soluble Fe(OH)(HL)2.3 H2O complex was also isolated. The reagent can be conveniently used as an indicator for the chelometric determination of iron.

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