scholarly journals Studying Acid-Base Equilibria in Two-Phase Solvent Media: Analyzing Results Using Aqueous Surfactant Solutions with Organic Solvents in the Titration of Analytes with Low Solubilities and Low Dissociation Constants

1993 ◽  
Vol 70 (1) ◽  
pp. 80 ◽  
Author(s):  
Sheryl A. Tucker ◽  
Vicki L. Amszi ◽  
William E. Acree
Keyword(s):  
Organic Solvents ◽  
Dissociation Constants ◽  
Acid Base ◽  
Two Phase ◽  
Surfactant Solutions

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 ACID-BASE PROPERTIES OF -UNSATURATED KETONES OBTAINED FROM REACTION OF 5-FORMYL-8-HYDROXYQUINOLINE WITH P-SUBSTITUTED ACETOPHENONES

2019 ◽  
Vol 16 (31) ◽  
pp. 755-764
Author(s):  
Roberto FERNANDEZ-MAESTRE ◽  
Alonso J MARRUGO-GONZÁLEZ
Keyword(s):  
Electron Donor ◽  
Opposite Effect ◽  
Dissociation Constants ◽  
Phenyl Group ◽  
Hydroxyl Group ◽  
Ultraviolet Spectroscopy ◽  
Acid Base ◽  
Unsaturated Ketones ◽  
Ph Values ◽  
Phenyl Fragment

Chalcones (α,β-unsaturated ketones) containing aromatic or heterocyclic radicals are highly reactive, allowing the synthesis of novel organic compounds. In this study, the dissociation constants (pKa) of seven chalcones derived from 8-hydroxyquinoline were determined and the influence on dissociation of substituents in the phenyl group (-CH3, -OCH3, -N(CH3)2, -Cl, -Br, and -NO2) was analysed. pKa values are important because they determine the pH at which ligands are fully deprotonated -when they show their maximum chelating properties- and determine the ligands interactions at different pH values. The chalcones’ pKa’s were calculated by visible ultraviolet spectroscopy in a water-ethanol (1:1) mixture using the Henderson-Hasselbach equation. It was shown that the 8-hydroxyquinolinic fragment has a large electron donor effect on the π system of the chalcones. The introduction of substituents (R) in the phenyl fragment of the chalcones slightly affected the dissociation of the hydroxyl group and the protonation of the nitrogen in the hydroxyquinoline fragment. The acceptor substituents (Cl, Br, NO2) increased the polarity of OH- and its acidity. Nitrogen protonation decreased electron donor properties of this fragment, and deprotonation of the hydroxyl caused the opposite effect. Substituents introduction in the phenyl fragment slightly affected hydroxyl group dissociation and nitrogen protonation.

scholarly journals pH modelling in aquatic systems with time-variable acid-base dissociation constants applied to the turbid, tidal Scheldt estuary

2009 ◽  
Vol 6 (8) ◽  
pp. 1539-1561 ◽  
Author(s):  
A. F. Hofmann ◽  
J. J. Middelburg ◽  
K. Soetaert ◽  
F. J. R. Meysman
Keyword(s):  
Dissolved Inorganic Carbon ◽  
Dissociation Constants ◽  
Time Variable ◽  
Scheldt Estuary ◽  
Biogeochemical Processes ◽  
Acid Base ◽  
Ph Profile ◽  
Proton Production ◽  
Co2 Degassing

Abstract. A new pH modelling approach is presented that explicitly quantifies the influence of biogeochemical processes on proton cycling and pH in an aquatic ecosystem, and which accounts for time variable acid-base dissociation constants. As a case study, the method is applied to investigate proton cycling and long-term pH trends in the Scheldt estuary (SW Netherlands, N Belgium). This analysis identifies the dominant biogeochemical processes involved in proton cycling in this heterotrophic, turbid estuary. Furthermore, information on the factors controlling the longitudinal pH profile along the estuary as well as long-term pH changes are obtained. Proton production by nitrification is identified as the principal biological process governing the pH. Its acidifying effect is mainly counteracted by proton consumption due to CO2 degassing. Overall, CO2 degassing generates the largest proton turnover in the whole estuary on a yearly basis. The main driver of long-term changes in the mean estuarine pH over the period 2001 to 2004 is the decreasing freshwater flow, which influences the pH directly via a decreasing supply of dissolved inorganic carbon and alkalinity, and also indirectly, via decreasing ammonia loadings and lower nitrification rates.

Spectrophotometric study of the effect of sodium dodecyl sulphate on the acid-base behaviour of 4-(2-pyridylazo)-resorcinol

1991 ◽  
Vol 56 (4) ◽  
pp. 785-795 ◽  
Author(s):  
Jiří Bílý ◽  
Ludmila Čermáková ◽  
Jiří Knapp
Keyword(s):  
Surface Tension ◽  
Critical Micelle Concentration ◽  
Sodium Dodecyl Sulphate ◽  
Azo Dye ◽  
Dissociation Constants ◽  
Sodium Dodecyl ◽  
Spectrophotometric Study ◽  
Acid Base ◽  
Strong Electrolytes ◽  
The Given

The values of the apparent dissociation constants of the azo dye 4-(2-pyridylazo)-resorcinol (PAR) have been found in the presence of sub- and supercritical concentrations of the anionogenic tenside sodium dodecyl sulphate (SDS) and the effects of the strong electrolytes NaCl and NaNO3 were also evaluated. In both electrolytes, the pKan values initially are independent of the SDS concentration and then increase. Spectrophotometric and surface tension measurements were employed to determine the critical micelle concentration (cmc) of SDS alone and in the presence of PAR and the given electrolytes. The determined cmc values were in the range 0.20–3.02 mmol l-1 and dependent on the type and concentration of the particular additive.

Glycosidases in organic solvents: I. Alkyl-β-glucoside synthesis in a water-organic two-phase system

1990 ◽  
Vol 12 (12) ◽  
pp. 950-954 ◽  
Author(s):  
Evgeni N. Vulfson ◽  
Rooma Patel ◽  
Jean E. Beecher ◽  
Anthony T. Andrews ◽  
Barry A. Law
Keyword(s):  
Organic Solvents ◽  
Phase System ◽  
Two Phase
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