Thermodynamic dissociation constants of benzoic and nitrobenzoic acids in mixtures of ethanol and 1-propanol with water at 25�C

1990 ◽  
Vol 19 (6) ◽  
pp. 623-638 ◽  
Author(s):  
M. S. K. Niazi ◽  
S. S. Shah ◽  
J. Ali ◽  
M. Z. I. Khan
Keyword(s):  
Dissociation Constants ◽  
Nitrobenzoic Acids

scholarly journals THE ACTIVATION OF STARFISH EGGS BY ACIDS

1927 ◽  
Vol 10 (5) ◽  
pp. 703-723 ◽  
Author(s):  
Ralph S. Lillie
Keyword(s):  
Carbonic Acid ◽  
Dissociation Constants ◽  
Free Acid ◽  
External Solution ◽  
Chlorobenzoic Acid ◽  
Nitrobenzoic Acid ◽  
Molecular Concentration ◽  
Nitrobenzoic Acids ◽  
Effective Component ◽  
Rate Of Activation

1. Comparison of the rates of activation of unfertilized starfish eggs in pure solutions of a variety of parthenogenetically effective organic acids (fatty acids, carbonic acid, benzoic and salicylic acids, chloro- and nitrobenzoic acids) shows that solutions which activate the eggs at the same rate, although widely different in molecular concentration, tend to be closely similar in CH. The dissociation constants of these acids range from 3.2 x 10–7 to 1.32 x 10–3. 2. In the case of each of the fourteen acids showing parthenogenetic action the rate of activation (within the favorable range of concentration) proved nearly proportional to the concentration of acid. The estimated CH of solutions exhibiting an optimum action with exposures of 10 minutes (at 20°) lay typically between 1.1 x 10–4 M and 2.1 x 10–4 M (pH = 3.7–3.96), and in most cases between 1.6 x 10–4 M and 2.1 x 10–4 M (pH = 3.7–3.8). Formic acid (CH = 4.2 x 10–4 M) and o-chlorobenzoic acid (CH = 3.5 x 10–4 M) are exceptions; o-nitrobenzoic acid is ineffective, apparently because of slow penetration. 3. Activation is not dependent on the penetration of H ions into the egg from without, as is shown by the effects following the addition of its Na salt to the solution of the activating acid (acetic, benzoic, salicylic). The rate of activation is increased by such addition, to a degree indicating that the parthenogenetically effective component of the external solution is the undissociated free acid. Apparently the undissociated molecules alone penetrate the egg freely. It is assumed that, having penetrated, they dissociate in the interior of the egg, furnishing there the H ions which effect activation. 4. Attention is drawn to certain parallels between the physiological conditions controlling activation in the starfish egg and in the vertebrate respiratory center.

Factors Influencing the Separation of Glu-Plasminogen Affinity Forms I and II by Affinity Chromatography

1984 ◽  
Vol 52 (03) ◽  
pp. 347-349 ◽  
Author(s):  
Daan W Traas ◽  
Bep Hoegee-de Nobel ◽  
Willem Nieuwenhuizen
Keyword(s):  
Affinity Chromatography ◽  
Dissociation Constants ◽  
Ionic Composition ◽  
Chloride Ions ◽  
Factors Influencing ◽  
Two Factors ◽  
Human Plasminogen

SummaryNative human plasminogen, the proenzyme of plasmin (E. C. 3.4.21.7) occurs in blood in two well defined forms, affinity forms I and II. In this paper, the feasibility of separating these forms of human native plasminogen by affinity chromatography, is shown to be dependent on two factors: 1) the ionic composition of the buffer containing the displacing agent: buffers of varying contents of sodium, Tris, phosphate and chloride ions were compared, and 2) the type of adsorbent. Two adsorbents were compared: Sepharose-lysine and Sepharose-bisoxirane-lysine. Only in the phosphate containing buffers, irrespective of the type of adsorbent, the affinity forms can be separated. The influence of the adsorbent can be accounted for by a large difference in dissociation constants of the complex between plasminogen and the immobilized lysine.

Determination of acidic dissociation constants of L-phenylalanyl-glycine and L-alanyl-L-alanine in water using ab initio methods

2014 ◽  
Vol 2 (42) ◽  
pp. 263-263
Author(s):  
Farhoush Kiani ◽  
Mahmoud Tajbakhsh ◽  
Fereydoon Ashrafi ◽  
Nesa Shafiei ◽  
Azar Bahadori ◽  
...  
Keyword(s):  
Ab Initio ◽  
Dissociation Constants ◽  
Ab Initio Methods ◽  
Acidic Dissociation

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.

Extraction of hafnium by means of some substituted 1-phenyl-3-methyl-4-benzoyl-pyrazol-5-ones

1981 ◽  
Vol 46 (8) ◽  
pp. 1901-1905 ◽  
Author(s):  
Oldřich Navrátil ◽  
Jiří Smola
Keyword(s):  
Ionic Strength ◽  
Aqueous Phase ◽  
Dissociation Constants ◽  
Parent Substance ◽  
Benzoyl Group ◽  
Extraction Constants ◽  
Extraction Parameters ◽  
Substituted 1

Distribution between aqueous phase and benzene or chloroform was studied for 1-phenyl-3-methyl-4-benzoylpyrazol-5-ones with 2-chloro, 4-methoxy, 3-nitro, and 4-nitro substitution in the benzoyl group (ionic strength of the aqueous phase 0.1) and for hafnium in their presence (ionic strength 2.0). The distribution and dissociation constants of the reagents and the extraction constants of their hafnium complexes were determined. Hafnium was found to be extracted as the HfA4 species. The extraction parameters of the derivatives in question do not differ substantially from those of the parent substance.

Biologically Important Physicochemical Properties of Some Cephalosporins

1992 ◽  
Vol 57 (8) ◽  
pp. 1739-1746
Author(s):  
Katarína Škvareninová ◽  
Štefan Baláž ◽  
Ernest Šturdík ◽  
Miroslav Veverka ◽  
Jana Adamcová ◽  
...  
Keyword(s):  
Physicochemical Properties ◽  
Partition Coefficients ◽  
Dissociation Constants ◽  
Transport Rate ◽  
Hydrolysis Rate ◽  
Antibacterial Effects ◽  
Oh Groups ◽  
Non Linear Equation ◽  
Cell Components ◽  
The Relationship

In the series of cephalosporin derivatives, consisting of eight 7-(R1-CH2-CO-NH)cephalosporanic acids and of seven analogical compounds with 3-acetoxymethyl replaced by 3-CH3, physicochemical properties, which are expected to play a role in their antibacterial effects (the transport rate parameters and partition coefficients in the systems 1-octanol-water and 1-octanol-buffer, dissociation constants of the 4-carboxyl group, reactivity towards L-glutathione imitating the nucleophilic groups of the cell components and hydrolysis rate parameters), were determined. Linear dependences were observed between the partition coefficients and the π-constants of the varying substituents as well as between reactivity towards SH-groups of L-glutathione and OH-groups. The relationship between the transport rate parameters and partition coefficients, both measured in buffered as well as non-buffered system, was described by a common non-linear equation.

Acids, bases and buffer solutions

2018 ◽  
Author(s):  
Dennis Sherwood ◽  
Paul Dalby
Keyword(s):  
First Principles ◽  
Buffer Capacity ◽  
Unique Feature ◽  
Dissociation Constants ◽  
Equilibrium Composition ◽  
Buffer Solutions ◽  
Acid And Base ◽  
Water Ph ◽  
Acids And Bases ◽  
Conjugate Bases

Many reactions in solution involve acids and bases, and so this chapter examines these important reactions in detail. Topics covered include the ionisation of water, pH, pOH, acids and bases, conjugate acids and conjugate bases, acid and base dissociation constants, the Henderson-Hasselbalch equation, the Henderson-Hasselbalch approximation, buffer solutions and buffer capacity. A unique feature of this chapter is a ‘first principles’ analysis of how a reaction buffered at a particular pH achieves an equilibrium composition different from that of the same reaction taking place in an unbuffered solution. This introduces some concepts which are important in understanding the biochemical standard state, as required for Chapter 23.

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