Measurement of the acidity function H0 of sulfo cation exchangers by the indicator method

1988 ◽  
Vol 37 (1) ◽  
pp. 39-43
Author(s):  
M. I. Vinnik ◽  
M. N. Gusev ◽  
V. V. Onishchenko
Keyword(s):  
Acidity Function ◽  
Indicator Method ◽  
Cation Exchangers

The H− acidity function for dimethylformamide–water

1970 ◽  
Vol 48 (21) ◽  
pp. 3354-3357 ◽  
Author(s):  
E. Buncel ◽  
E. A. Symons ◽  
Douglas Dolman ◽  
Ross Stewart
Keyword(s):  
Solvent System ◽  
Tetramethylammonium Hydroxide ◽  
Acidity Function ◽  
Hydroxide Ion ◽  
Indicator Method ◽  
Aqueous Dimethylsulfoxide

The H− acidity function has been determined for N,N-dimethylformamide–water mixtures containing tetramethylammonium hydroxide by the Hammett indicator method. Basicity in the aqueous dimethylformamide system exceeds that in aqueous tetramethylenesulfone but is slightly less than in aqueous dimethylsulfoxide, at equivalent molar compositions of solvent and base. However, the basic aqueous dimethylformamide solvent system is only of limited utility as a result of reaction of hydroxide ion with the dimethylformamide.

scholarly journals The Proton Dissociation of Bio-Protic Ionic Liquids: [AAE]X Amino Acid Ionic Liquids

Molecules ◽  
2020 ◽  
Vol 26 (1) ◽  
pp. 62
Author(s):  
Ting He ◽  
Cheng-Bin Hong ◽  
Peng-Chong Jiao ◽  
Heng Xiang ◽  
Yan Zhang ◽  
...  
Keyword(s):  
Ionic Liquids ◽  
Amino Acid ◽  
Acid Ester ◽  
Amino Acid Ester ◽  
Acidity Function ◽  
Brønsted Acidity ◽  
Protic Ionic Liquids ◽  
Indicator Method ◽  
Pka Values ◽  
Brönsted Acidity

[AAE]X composed of amino acid ester cations is a sort of typically “bio-based” protic ionic liquids (PILs). They possess potential Brønsted acidity due to the active hydrogens on their cations. The Brønsted acidity of [AAE]X PILs in green solvents (water and ethanol) at room temperature was systematically studied. Various frameworks of amino acid ester cations and four anions were investigated in this work from the viewpoint of structure–property relationship. Four different ways were used to study the acidity. Acid dissociation constants (pKa) of [AAE]X determined by the OIM (overlapping indicator method) were from 7.10 to 7.73 in water and from 8.54 to 9.05 in ethanol. The pKa values determined by the PTM (potential titration method) were from 7.12 to 7.82 in water. Their Hammett acidity function (H0) values (0.05 mol·L−1) were about 4.6 in water. In addition, the pKa values obtained by the DFT (proton-transfer reactions) were from 7.11 to 7.83 in water and from 8.54 to 9.34 in ethanol, respectively. The data revealed that the cationic structures of [AAE]X had little effect and the anions had no effect on the acidity of [AAE]X. At the same time, the OIM, PTM, Hammett method and DFT method were reliable for determining the acidic strength of [AAE]X in this study.

The Effect of Partly Missing Covariates on Statistical Power in Randomized Controlled Trials With Discrete-Time Survival Endpoints

Methodology ◽  
2017 ◽  
Vol 13 (2) ◽  
pp. 41-60
Author(s):  
Shahab Jolani ◽  
Maryam Safarkhani
Keyword(s):  
Randomized Controlled Trials ◽  
Discrete Time ◽  
Treatment Effect ◽  
Survival Data ◽  
Controlled Trials ◽  
Missing Covariates ◽  
Indicator Method ◽  
Imputation Methods ◽  
Randomized Controlled ◽  
Baseline Covariates

Abstract. In randomized controlled trials (RCTs), a common strategy to increase power to detect a treatment effect is adjustment for baseline covariates. However, adjustment with partly missing covariates, where complete cases are only used, is inefficient. We consider different alternatives in trials with discrete-time survival data, where subjects are measured in discrete-time intervals while they may experience an event at any point in time. The results of a Monte Carlo simulation study, as well as a case study of randomized trials in smokers with attention deficit hyperactivity disorder (ADHD), indicated that single and multiple imputation methods outperform the other methods and increase precision in estimating the treatment effect. Missing indicator method, which uses a dummy variable in the statistical model to indicate whether the value for that variable is missing and sets the same value to all missing values, is comparable to imputation methods. Nevertheless, the power level to detect the treatment effect based on missing indicator method is marginally lower than the imputation methods, particularly when the missingness depends on the outcome. In conclusion, it appears that imputation of partly missing (baseline) covariates should be preferred in the analysis of discrete-time survival data.

Indicators of Sustainable Development of the Province of Warmia and Mazury in the Environmental Aspect

2016 ◽  
Vol 11 (3) ◽  
pp. 299-309
Author(s):  
Mirosława Witkowska-Dąbrowska
Keyword(s):  
Quality Of Life ◽  
Sustainable Development ◽  
Data Bank ◽  
Local Data ◽  
Indicator Method ◽  
Environmental Aspect ◽  
The Sustainable Development ◽  
Assessment Indicator ◽  
Area Unit

The purpose of this study has been to identify the degree of sustainability in the development of the Province of Warmia and Mazury. The theoretical and empirical investigations were conducted between 2003-2014 based on data from the Local Data Bank. Using a comparative indicator method, 20 indicators were developed, with different directions of preference. The evaluation involves the concept of uniform preference, hence the higher the assessment indicator, the better the situation in the evaluated area unit. Our studies on the sustainable development of the Province of Warmia and Mazury suggest that the indicators measuring the environmental dimension and consequently the quality of life of the residents (in this aspect) score higher than the country's average values. It is also optimistic that some progress, however small, can be seen in this area based on the analyzed dynamics of changes.

Preparation and Characterization of a Novel Room Temperature Dicationic Ionic Liquid and its Application in the Synthesis of Xanthenediones Under Solvent-Free Conditions

2018 ◽  
Vol 21 (8) ◽  
pp. 602-608 ◽  
Author(s):  
Zainab Ehsani-Nasab ◽  
Ali Ezabadi
Keyword(s):  
Ionic Liquid ◽  
Room Temperature ◽  
Reaction Times ◽  
Significant Loss ◽  
Solvent Free ◽  
Acidity Function ◽  
Efficient Catalyst ◽  
Solvent Free Conditions ◽  
Hammett Acidity Function ◽  
Dicationic Ionic Liquid

Aim and Objective: In the present work, 1, 1’-sulfinyldiethylammonium bis (hydrogen sulfate) as a novel room temperature dicationic ionic liquid was synthesized and used as a catalyst for xanthenediones synthesis. Material and Method: The dicationic ionic liquid has been synthesized using ethylamine and thionyl chloride as precursors. Then, by the reaction of [(EtNH2)2SO]Cl2 with H2SO4, [(EtNH2)2SO][HSO4]2 was prepared and after that, it was characterized by FT-IR, 1H NMR, 13C NMR as well as Hammett acidity function. This dicationic ionic liquid was used as a catalyst for the synthesis of xanthenediones via condensation of structurally diverse aldehydes and dimedone under solvent-free conditions. The progress of the reaction was monitored by thin layer chromatography (ethyl acetate/n-hexane = 3/7). Results: An efficient solvent-free method for the synthesis of xanthenediones has been developed in the presence of [(EtNH2)2SO][HSO4]2 as a powerful catalyst with high to excellent yields, and short reaction times. Additionally, recycling studies have demonstrated that the dicationic ionic liquid can be readily recovered and reused at least four times without significant loss of its catalytic activity. Conclusion: This new dicationic ionic liquid can act as a highly efficient catalyst for xanthenediones synthesis under solvent-free conditions.

Solvolysis kinetics and mechanism of substituted 3-acetyl-1,3-diphenyltriazenes in acid medium; Kinetic acidity function

1987 ◽  
Vol 52 (9) ◽  
pp. 2212-2216
Author(s):  
Oldřich Pytela ◽  
Martin Kaska ◽  
Miroslav Ludwig ◽  
Miroslav Večeřa
Keyword(s):  
Acid Medium ◽  
Sulphuric Acid ◽  
Rate Constants ◽  
Decomposition Kinetics ◽  
Acidity Function ◽  
Hammett Equation ◽  
Kinetic Acidity ◽  
Reaction Constant ◽  
Acid Catalyzed ◽  
Catalytic Rate

The decomposition kinetics has been measured of fourteen 3-acetyl-1,3-bis(subst. phenyl)triazenes in 40% (v/v) ethanol and sulphuric acid. The kinetic acidity function and catalytic rate constants have been determined from the rate constants observed. Mechanism has been suggested for the general acid-catalyzed solvolysis from comparison of the course of the kinetic acidity function and H0 function and from the reaction constant of the Hammett equation.

Preparation of Strong Acid Catalysts by Sulfate Treatment of Calcined Boehmite

1992 ◽  
Vol 57 (11) ◽  
pp. 2241-2247 ◽  
Author(s):  
Tomáš Hochmann ◽  
Karel Setínek
Keyword(s):  
Catalytic Activity ◽  
Surface Area ◽  
Aluminum Sulfate ◽  
Solid Acid ◽  
Strong Acid ◽  
Acid Strength ◽  
Solid Acid Catalysts ◽  
Acid Catalysts ◽  
Preparation Methods ◽  
Indicator Method

Solid acid catalysts with acid strength of -14.52 < H0 < -8.2 were prepared by sulfate treatment of the samples of boehmite calcined at 105-800 °C. Two preparation methods were used: impregnation of the calcined boehmite with 3.5 M H2SO4 or mixing of the boehmite samples with anhydrous aluminum sulfate, in both cases followed by calcination in nitrogen at 650 °C. The catalysts were characterized by measurements of surface area, adsorption of pyridine and benzene, acid strength measurements by the indicator method and by catalytic activity tests in the isomerization of cyclohexene, p-xylene and n-hexane. Properties of the catalysts prepared by both methods were comparable.

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