scholarly journals Potentiometric pKa determination of biological active phenothiazine in different aqua-organic solvents

2020 ◽  
Vol 13 (1) ◽  
pp. 25-29
Author(s):  
Tanaji N. Bansode
Keyword(s):  
Dielectric Constant ◽  
Ionic Strength ◽  
Organic Solvent ◽  
Dissociation Constant ◽  
Organic Solvents ◽  
Organic Medium ◽  
Effect Of Temperature ◽  
Different Temperatures ◽  
Pka Determination

Potentiometric titrations of phenothiazines derivatives were performed in methanolwater, ethanol-water, acetonitrile-water and dioxane-water mixtures with varying contents of organic solvent. All titrations were performed in aqua-organic medium at constant ionic strength (0.15 mol⋅dm−3) and at different temperatures (25 to 45 °C). The pKa were determined at different aqua-organic proportions. Effect of temperature and dielectric constant on dissociation constant has been compared. The pKa values were then obtained by Yasuda‐Shedlovsky extrapolation.

scholarly journals On the direct determination of the electrostatic moments of molecules

1929 ◽  
Vol 124 (795) ◽  
pp. 689-698 ◽  
Keyword(s):  
Dielectric Constant ◽  
Direct Determination ◽  
Negative Temperature ◽  
Dielectric Constants ◽  
Temperature Coefficients ◽  
Different Temperatures

According to Faraday's ideas, the specific inductive capacity of a substance is due to the polarisation of the molecules as wholes. This is the basis of the old Clausius-Mosotti theory of dielectrics, on which it is shown first that the polarisation P is proportional to the polarising field, i. e. , P = k E, k being the dielectric constant, and second that δ being the density of the dielectric, k - 2/ k + 2 ·1/δ = constant. Now it is known that some substances have large negative temperature coefficients for their dielectric constants which cannot thus be accounted for. To provide for this Debye proposed the theory that the molecules were permanently polarised and that they were systematically orientated in the field. This leads to the equation k - 2/ k + 2 = a T -1 + b T -2 , to represent the change of specific inductive capacity with temperature. This theory has been developed by Gans and others, and a number of measurements have been made by Smyth and others, who have found the molecular moments of many substances by measuring the dielectric constants at different temperatures.

THE REACTION BETWEEN CYANATE AND HYPOCHLORITE

1956 ◽  
Vol 34 (4) ◽  
pp. 489-501 ◽  
Author(s):  
M. W. Lister
Keyword(s):  
Activation Energy ◽  
Ionic Strength ◽  
Rate Constant ◽  
Hypochlorous Acid ◽  
Effect Of Temperature ◽  
Slow Step ◽  
True Activation Energy ◽  
Rate Of Reaction ◽  
Different Temperatures ◽  
Kinetics Of

The reaction between sodium hypochlorite and potassium cyanate in the presence of sodium hydroxide has been examined. The main products are chloride, and carbonate ions and nitrogen; but, especially if much hypochlorite is present, some nitrate is formed as well. The rate of reaction is proportional to the cyanate and hypochlorite concentrations, but inversely proportional to the hydroxide concentration: the rate constant is 5.45 × 10−4 min.−1 at 65 °C, at an ionic strength of 2.2. The rate constant increases somewhat as the ionic strength rises from 1.7 to 3.5. The effect of temperature makes the apparent activation energy 25 kcal./gm-molecule. The kinetics of the reaction suggest that the slow step is really a reaction of hypochlorous acid and cyanate ions, and possible intermediate products of this reaction are suggested. Allowing for the different extent of hydrolysis of hypochlorite at different temperatures, the true activation energy is found to be 15 kcal./gm-mol., which is consistent with the observed rate of reaction.

scholarly journals PENGARUH TEMPERATUR TERHADAP PERKEMBANGAN NEMATODA SISTA KENTANG (GLOBODERA SPP.) INDONESIA

2010 ◽  
Vol 10 (1) ◽  
pp. 29-34
Author(s):  
Lisnawita Lisnawita ◽  
Meity S. Sinaga ◽  
Supramana Supramana ◽  
Gede Suastika
Keyword(s):  
Cyst Nematode ◽  
Potato Cyst Nematode ◽  
Effect Of Temperature ◽  
Multiplication Rate ◽  
Optimum Temperature ◽  
Central Java ◽  
Major Constraint ◽  
Different Temperatures ◽  
Reproduction Factor

The effect of temperature on the development of Indonesian potato cyst nematode.  Potato cyst nematode (PCN) is a serious pathogen of potato and is found in most potato producing areas of the world.  In Indonesia, PCN was recently discovered and recognized as major constraint on potato.  The growth and behaviour of nematodes are affected by the environment.  Therefore, determination of the biology of PCN Indonesian populations is urgently needed to manage this pathogens effectively.  The effect of temperature on biology factors of four PCN Indonesian populations (North Java 1, North Java 2, West Java, and Central Java) was studied at different temperatures levels (12, 15, 18, 21 and 24ºC) in the growth chamber.  The aim of this research was to study the effect of temperature on development of PCN.  Observation was conducted on cyst number, reproduction factor (Rf), survival, fecundity and multiplication of PCN.   The optimum temperature range for maximum cysts production with the highest reproduction factor, survival, fecundity and multiplication rate for all populations was 15 - 21ºC.  The hatching and development of all PCN populations reduced at temperature below 15ºC or above 21ºC.

scholarly journals Development of Methods for the Determination of pKa Values

2013 ◽  
Vol 8 ◽  
pp. ACI.S12304 ◽  
Author(s):  
Jetse Reijenga ◽  
Arno van Hoof ◽  
Antonie van Loon ◽  
Bram Teunissen
Keyword(s):  
Dissociation Constant ◽  
Conceptual Development ◽  
Acid Dissociation ◽  
Acid Dissociation Constant ◽  
Future Developments ◽  
Research Fields ◽  
Current State ◽  
Wide Range ◽  
Pka Determination

The acid dissociation constant (pKa) is among the most frequently used physicochemical parameters, and its determination is of interest to a wide range of research fields. We present a brief introduction on the conceptual development of pKa as a physical parameter and its relationship to the concept of the pH of a solution. This is followed by a general summary of the historical development and current state of the techniques of pKa determination and an attempt to develop insight into future developments. Fourteen methods of determining the acid dissociation constant are placed in context and are critically evaluated to make a fair comparison and to determine their applications in modern chemistry. Additionally, we have studied these techniques in light of present trends in science and technology and attempt to determine how these trends might affect future developments in the field.

Kinetics of the Alkaline Solvolysis of Trichloroacetate Ion in Water-Ethanol Solutions

1978 ◽  
Vol 33 (1) ◽  
pp. 30-34
Author(s):  
I. M. Issa ◽  
E . M. Diefallah ◽  
M. R. Mahmoud ◽  
A. M. El-Nady
Keyword(s):  
Dielectric Constant ◽  
Organic Solvent ◽  
Transition State ◽  
Trichloroacetic Acid ◽  
Reaction Rate ◽  
Water Solvent ◽  
Different Temperatures ◽  
Kinetics Of ◽  
Activated Complex ◽  
Polar Water

Abstract Alkaline Solvolysis, Trichloroacetate Ion The alkaline solvolysis of trichloroacetic acid in water-ethanol mixtures have been studied in the presence of 0.40-0.80 M sodium hydroxide within the temperature range 35-70 °C. The rate constant increased with progressive addition of the organic solvent. The dielectric constant effect on the reaction rate was investigated. The radius of the activated complex at different temperatures was calculated. The isocomposition and isodielectric energies as well as the thermodynamic parameters of activation were calculated and their significance in terms of solvent composition has been discussed. It was concluded that the reactant state is extensively higher solvated than the transition state by the highly polar (water) solvent.

scholarly journals Overview on chromatographic and potentiometric based approaches for pKa determination of sparingly soluble substances

2018 ◽  
Vol 63 (02) ◽  
pp. 21-27
Author(s):  
Natalija Nakov ◽  
Jelena Acevska ◽  
Katerina Brezovska ◽  
Aneta Dimitrovska
Keyword(s):  
Dissociation Constant ◽  
Active Pharmaceutical Ingredients ◽  
Calculation Methods ◽  
Reverse Phase ◽  
Pharmaceutical Ingredients ◽  
Reverse Phase Liquid Chromatography ◽  
Rp Hplc ◽  
Pka Determination ◽  
Phase Liquid

The dissociation constant (pKa) is one of the most important physicochemical property of the compounds and it is of great importance for the pharmaceutical industry. Many of the active pharmaceutical ingredients are sparingly soluble in water or have no chromophore, thus the conventional UV/Vis spectrometry and potentiometry methods are not applicable. This article presents an overview of several approaches based on RP-HPLC and cosolvent/surfactant potentiometry that have been recently published for the pKa determination of sparingly soluble active pharmaceutical ingredients. Additionally, different calculation methods that have been used for the estimation of the aqueous dissociation constant are summarized. Keywords: dissociation constant, pKa, sparingly soluble substances, determination, reverse-phase liquid chromatography, potentiometry, surfactants

Dispersive liquid–liquid microextraction with back extraction using an immiscible organic solvent for determination of benzodiazepines in water, urine, and plasma samples

RSC Advances ◽  
2016 ◽  
Vol 6 (115) ◽  
pp. 114198-114207 ◽  
Author(s):  
Mahnaz Ghambarian ◽  
Fateme Tajabadi ◽  
Yadollah Yamini ◽  
Ali Esrafili
Keyword(s):  
Organic Solvent ◽  
Organic Solvents ◽  
Back Extraction ◽  
Plasma Samples ◽  
Extraction Step ◽  
Dispersive Liquid Liquid Microextraction ◽  
Liquid Microextraction

A novel DLLME method with a back extraction step using two immiscible organic solvents for obtaining higher clean-up than the conventional DLLME method.

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