Acid-base equilibria of some 7-dimethylamino-3-phenoxazone derivatives

1982 ◽  
Vol 47 (6) ◽  
pp. 1588-1596 ◽  
Author(s):  
Vladimír Dostál ◽  
Milan Kotouček ◽  
Hana Kalašová ◽  
Vladimíra Bryndová ◽  
Jiří Šimek
Keyword(s):  
Methyl Ester ◽  
Dissociation Constants ◽  
Spectral Characteristics ◽  
Acid Base ◽  
Protolytic Reactions ◽  
Colour Changes ◽  
Reagent Grade Purity

The acid-base equilibria of some phenoxazine dyes in aqueous-ethanolic solutions were studied spectrophotometrically. The compounds examined were prepared in reagent grade purity, their main spectral characteristics in UV and VIS reagion were found and their dissociation constants were determined in 41% (m/m) ethanol. For the analytically most interesting derivative, gallocyanine methyl ester (IV), the pK values were measured also in solutions with different proportions of ethanol. The colour changes accompanying the protolytic reactions and the factors governing the phenomena are discussed.

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.

UV and IR Spectral Characteristics of Chloramben in Selected Environments

Weed Science ◽  
1976 ◽  
Vol 24 (1) ◽  
pp. 107-114 ◽  
Author(s):  
V. E. Berkheiser ◽  
J. L. Ahlrichs
Keyword(s):  
Ir Spectra ◽  
Water Content ◽  
Absorption Spectra ◽  
Spectral Characteristics ◽  
Uv Absorption ◽  
Hydration Water ◽  
Carboxyl Group ◽  
Amino Group ◽  
Acid Base ◽  
Uv Absorption Spectra

Ultraviolet (UV) absorption spectra were recorded of chloramben (3-amino-2,5-dichlorobenzoic acid) and selected relatives in solutions of different pH's. From these spectra, the Broensted acid-base properties of chloramben were deduced. Interpretations of solution spectra were applied to UV absorption spectra of chloramben adsorbed onto Ca-montmorillonite at low water content. Infrared (IR) transmittance spectra were recorded of chloramben and selected derivatives in KBr pellets and band assignments were made. Interpretations of these spectra were also applied to IR spectra of chloramben adsorbed onto Ca-montmorillonite at low water content. Both UV and IR measurements indicated that protonation of the amino group occurs and that the carboxyl group of chloramben is strongly hydrogen-bonded to the hydration water of the interlayer cations.

235 THE EFFECTS OF NG-NITRO L-ARGININE METHYL ESTER (L-NAME) ON ACID-BASE STATUS IN ARTERIAL AND VENOUS BLOOD IN HEMORRHAGIC SHOCK

Shock ◽  
1995 ◽  
Vol 3 (5) ◽  
pp. 73
Author(s):  
G. Zunic ◽  
Z. Todorović ◽  
M. Prostran ◽  
S. Vujnov ◽  
J. Savić ◽  
...  
Keyword(s):  
Methyl Ester ◽  
Hemorrhagic Shock ◽  
Venous Blood ◽  
Acid Base ◽  
Acid Base Status

scholarly journals Acid dissociation constants of glycopeptides

1977 ◽  
Vol 163 (1) ◽  
pp. 31-38 ◽  
Author(s):  
B M Austen ◽  
R D Marshall
Keyword(s):  
Amino Acid ◽  
Dissociation Constants ◽  
Acid Dissociation ◽  
Hydroxyl Group ◽  
Amino Acid Residues ◽  
Acid Base ◽  
Titration Curves ◽  
Pka Value ◽  
Hen’S Egg ◽  
Additional Amino Acid

Glycopeptides containing mainly four amino acid residues in the sequence Asn-Leu-Thr-Ser, with small amounts of additional amino acid residues, were isolated from enzymic hydrolysates of hen's-egg albumin. Heterogeneity of the carbohydrate moiety was confirmed. Acid-base titrations showed that the alpha-amino group has a pKa value of 6.43 at 25 degrees C. The standard free engery and entropy changes associated with the ionization at 25 degrees C were 37.2kJ-mol-1 and -0.014kJ-mol-1- K-1 respectively. The complications arising in the interpretation of titration curves of the glycopeptides, which are heterogeneous with respect to the peptide chain, were considered and discussed in the light of the earlier suggestion that the titration curve of the glycopeptide might be interpreted as being due in part to a structure in which the hydroxyl group of the threonine residue is hydrogen-bonded to the beta-aspartamido oxygen atom [Neuberger & Marshall (1968) in Symposium on Foods - Carbohydrates and their Roles (Schultz, H.W., Cain, R.F. & Wrolstad, R.W., eds.), pp. 115-132, Avi Publishing Co., Westport, CT]. It is concluded that either the glycopeptides do not contain a hydrogen bond of that type, or, if they do, that it cannot be recognized by acid-base-titration studies.

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