A potentiometric study of the effects of molecular complexing on acid–base equilibria

1976 ◽  
Vol 54 (13) ◽  
pp. 2141-2153 ◽  
Author(s):  
A. K. Colter ◽  
D. Buben
Keyword(s):  
Electrostatic Interactions ◽  
Potentiometric Method ◽  
Acidity Constant ◽  
Complexation Constants ◽  
Acid Base ◽  
Acid Complex ◽  
Molecular Complexation ◽  
Opposing Effects ◽  
Conjugate Base ◽  
Sufficient Precision

The effect of molecular complexing on several acid–base equilibria involving organic π donor acids has been studied by a potentiometric method. The method leads to complexation constants for the acceptor with the donor acid and its conjugate base. In several cases the two association constants can be determined with sufficient precision to obtain an estimate of the acidity constant for the 1:1 acceptor–donor acid complex. In all situations where charge-transfer and electrostatic interactions are expected to have opposing effects on the acidity, electrostatic effects dominate. The range of the validity and usefulness of the potentiometric method in studies of molecular complexation equilibria is discussed, together with the results obtained in this work.

Electrostatic Interactions between Acid-/Base-Containing Polymer Nanoparticles and Proteins: Impact of Polymerization pH

2020 ◽  
Vol 3 (6) ◽  
pp. 3827-3834 ◽  
Author(s):  
Ryutaro Honda ◽  
Tomohiro Gyobu ◽  
Hideto Shimahara ◽  
Yoshiko Miura ◽  
Yu Hoshino
Keyword(s):  
Electrostatic Interactions ◽  
Polymer Nanoparticles ◽  
Acid Base

Effect of anemia on oxygen transport in hemorrhagic shock

1979 ◽  
Vol 47 (4) ◽  
pp. 882-888 ◽  
Author(s):  
P. O. Malmberg ◽  
R. D. Woodson
Keyword(s):  
Hemorrhagic Shock ◽  
Oxygen Transport ◽  
Exchange Transfusion ◽  
Acid Base Balance ◽  
Acid Base ◽  
Bleeding Rate ◽  
Shed Blood ◽  
Oxygen Capacity ◽  
Base Balance ◽  
Opposing Effects

Effect of anemia on tolerance of hemorrhagic shock in rats was studied to examine opposing effects of altered oxygen capacity and viscosity on oxygen delivery at reduced blood flow. Hematocrit was first reduced by exchange transfusion. Hypotension (BP = 30 Torr) was induced and maintained at this level by controlled hemorrhage; it was terminated when reinfusion of shed blood became necessary to sustain this blood pressure. The period of compensation (time at 30 Torr until reinfusion) in control rats (Hct = 42.5 +/- 2.7%) was 59.23 min; in anemic rats (Hct = 23.3 +/- 2.2%) it was 53 +/- 15 min (SD, P = 0.086). Bleeding rate during shock, mortality, VO2, acid-base balance, and mortality were not influenced by anemia, except for slightly higher lactate in late shock in anemia. The lack of influence of anemia (cf. other perturbations of oxygen transport) was apparently due to a 59–88% increase in cardiac ouput during shock in anemia, which maintained VO2.

scholarly journals USING POTENTIOMETRIC ACID-BASE TITRATION TO DETERMINE PKA FROM MANGOSTEEN PERICARPS EXTRACT

2019 ◽  
Vol 16 (32) ◽  
pp. 768-773
Author(s):  
L. TANIA ◽  
C. DIAWATI ◽  
M. SETYARINI ◽  
N. KADARITNA ◽  
A. SAPUTRA
Keyword(s):  
Oxalic Acid ◽  
Potentiometric Titration ◽  
Accurate Determination ◽  
Acidity Constant ◽  
Equivalence Point ◽  
Acid Base ◽  
Titrant Volume ◽  
Acid Base Titration ◽  
Ph Range

One of the uses of acid-base indicators is to show the end point of the titration, so the accurate determination of acidity constant and pH range of indicators needs to be done. This study aims to determine the acidity constant (pKa) of mangosteen pericarp extract and its accuracy as an indicator of acid-base titration. Determination of pKa was done by a simple potentiometric titration method. The titration data were plotted in three graphs, i.e., pH, ΔpH/ΔV (the (the first derivative), and Δ2pH/ΔV2 (the second derivative) versus titrant volume to determine the equivalence point of the titration. The accuracy test was carried out by comparing the volume of oxalic acid used to titrate NaOH solution using the indicator of mangosteen pericarp extract and phenolphthalein indicator. The result showed that the equivalence point was found on the titrant volume of 8.6 mL and a measured pH of 9.84. so the pKa value of mangosteen pericarp extract was 7.20, and the pH range was 6.20 to 8.20. the average volume of oxalic acid used to titrate 5 mL of NaOH using phenolphthalein as the indicator was 5.2 mL while the titration used mangosteen pericarp extract was 5.23 mL. The accuracy of mangosteen pericarp extract was 99.42%. By the result, it can be concluded that potentiometric titration can be used as a simple way to determine the acidity constant of mangosteen pericarp extract. Moreover, the mangosteen pericarp extract can be used as an alternative acid-base titration indicator to substitute the common acid-base titration in the laboratory.

scholarly journals SYNTHESIS, COORDINATION AND ACID-BASE PROPERTIES OF MESO-DINITROSUBSTITUTED DERIVATIVES OF 5,15-DIPHENYL-β-OCTAALKYLPORPHINE

2018 ◽  
Vol 61 (6) ◽  
pp. 17
Author(s):  
Svetlana G. Pukhovskaya ◽  
Yulia B. Ivanova ◽  
Dmitry A. Erzunov ◽  
Aleksander S. Semeykin ◽  
Sergei A. Syrbu
Keyword(s):  
Spectral Characteristics ◽  
Spectrophotometric Titration ◽  
Basicity Constant ◽  
Acidity Constant ◽  
Electronic Effects ◽  
Acid Base ◽  
Electronic Effects Of Substituents ◽  
Derivatives Of ◽  
Base Properties

Presented work shows results of synthesis and spectrophotometric researches on properties of meso-dinitrosubstituted derivatives of 5,15-diphenyl-β-octaalkylporphyrin nitroderivatives in comparison with 2,8,12,18,3,7,13,17-octaethylporphyrin and 2,3,7,8,12,13,17,18-octaethyl-5,15-dinitroporphyrin. The method of spectrophotometric titration with perchloric acid (for determining the basicity constant) and 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU) was used in order to study the acid-base properties of porphyrins, namely to determine the acidity constant. The spectral characteristics of the ionized forms of 5,15-dinitro-10,20-diphenyl-3,7,13,17-tetramethyl-2,8,12,18-tetraethylporfin-F (I) and 5,15-dinitro-10,20-bis(4-nitrophenyl)-2,8,12,18-tetramethyl-3,7,13,17-tetraethylporphyrin (II) and the corresponding total constants of the acidic (pKa (I) = 6.00 and pKa (II) = 5.27) and the basic (pKb (I) = 19.78 and pKb (II) = 19.83) ionization were provided. The reaction of complexation of porphyrins with zinc acetate was studied by spectrophotometric method in pure acetonitrile and in mixed AN + DBU solvent. The influence of the degree of deformation of the tetrapyrrole macroring, the electronic effects of substituents and the acidity of the medium on the coordination and acid-base properties of porphyrins was analyzed. It was shown that the reactions of formation of metalloporphyrins with anionic porphyrin forms proceed with much higher rates compared to molecular ones, that is accompanied with a decrease in the energy parameters of the reaction. This is evidently due to the absence of energy costs for the deformation and cleaving N-H bonds of the reaction center, as well as the stronger polarization of the molecule, and as a consequence, the higher degree of solvation of anionic forms of porphyrins in the transition state. Thus, the determination of the conditions for the existence of dianionic forms of porphyrins gives grounds for the development of new sensor systems for the recognition and determination of the concentration of metal cations in liquid media due to a sharp increase in the rate of formation of metalloporphyrins in the presence of an organic base.Forcitation:Pukhovskaya S.G., Ivanova Yu.B., Erzunov D.A., Semeykin A.S., Syrbu S.A. Synthesis, coordination and acid-base properties of meso-dinitrosubstituted derivatives of 5,15-diphenyl-β-octaalkylporphine. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 6. P. 17-28

scholarly journals An ultra-stable oxoiron(iv) complex and its blue conjugate base

2014 ◽  
Vol 5 (3) ◽  
pp. 1204-1215 ◽  
Author(s):  
Jason England ◽  
Jennifer O. Bigelow ◽  
Katherine M. Van Heuvelen ◽  
Erik R. Farquhar ◽  
Marléne Martinho ◽  
...  
Keyword(s):  
Base Pair ◽  
Carbonyl Oxygen ◽  
Acid Base ◽  
Conjugate Acid ◽  
Conjugate Base

We report the first conjugate acid–base pair of nonheme oxoiron(iv) complexes, which are supported by a tetramethylcyclam ligand with a pendant amide that binds trans to the oxo group via the carbonyl oxygen.

On the Role of Electrostatic Interactions in Stabilization of Oxidized Nucleic Acid Base Complexes

2009 ◽  
Author(s):  
Ż. Czyżnikowska ◽  
R. Zaleśny ◽  
M. G. Papadopoulos ◽  
George Maroulis ◽  
Theodore E. Simos
Keyword(s):  
Nucleic Acid ◽  
Electrostatic Interactions ◽  
Acid Base ◽  
Nucleic Acid Base

scholarly journals Protolytic equilibria in homogeneous and heterogeneous systems of ketoconazole and its direct spectrophotometric determination in tablets

2005 ◽  
Vol 70 (1) ◽  
pp. 67-78 ◽  
Author(s):  
Mirjana Vojic ◽  
Gordana Popovic ◽  
Dusan Sladic ◽  
Lidija Pfendt
Keyword(s):  
Ionic Strength ◽  
Spectrophotometric Determination ◽  
Spectrophotometric Method ◽  
Equilibrium Constants ◽  
Heterogeneous Systems ◽  
Water Systems ◽  
Acidity Constant ◽  
Acid Base ◽  
Protolytic Equilibria

The acid-base equilibria of a diprotic, slightly hydrosoluble base ketoconazole were studied in homogeneous and heterogeneous water systems. The determinations were performed at 25?C at a constant ionic strength of M(NaCl). The acidity constant Ka1 was determined by potentiometric (pKa1 3.20) and spectrophotometric (pKa1 3.26) methods. A pKa2 constant of 6.10 was obtained based on the equilibrium constants pKs0 4.84 and pKs1 -1.26, determined in a heterogeneous ketoconazole system. The obtained values of the constants served to calculate the solubility and the distribution of the equilibrium forms of ketoconazole as a function of pH. On the basis of the distribution of the equilibrium forms of ketoconazole, a spectrophotometric method for the determination of its content in commercial tablets was developed. The determinations were performed at 225 nm in 0.1 M HCl. The method is simple and rapid and enables the direct spectrophotometric determination of the content of ketoconazole without previous isolation.

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