scholarly journals Beiträge zur Chemie des Phosphors, 139 [1] Triethyl-cyclotriphosphan, Trimethyl-cyclotriphosphan; Gleichgewichte zwischen Cyclophosphanen (PR)n bei erhöhten Temperaturen/Contributions to the Chemistry of Phosphorus, 139 [1] Triethylcyclotriphosphane, Trimethylcyclotriphosphane; Equilibria between Cyclophosphanes (PR)n at Elevated Temperatures

1984 ◽  
Vol 39 (4) ◽  
pp. 438-444 ◽  
Author(s):  
Marianne Baudler ◽  
Josef Hahn ◽  
Erwin Clef
Keyword(s):  
Thermodynamic Equilibrium ◽  
Thermodynamic Data ◽  
Elevated Temperatures ◽  
Equilibrium Constants ◽  
Fractional Distillation ◽  
Ring Strain ◽  
Product Mixture

Triethylcyclotriphosphane, (PEt)3 (1), has been generated by thermolysis of tetraethylcyclotetraphosphane, (PEt)4. 1 can be obtained as a 43% solution in 1,2,3-triethyl-1,2,3-triphosphole, (PEt)3C2H2 (3), by fractional distillation of the product mixture formed in the reaction of K2(PEt)4 with ClHC=CHCl. 3 has been isolated and fully characterized. Furthermore 1 as well as (PMe)3 (2) and (PPh)3 exist besides (PR)4 (R = Et, Me, Ph) in thermodynamic equilibrium with (PR)5 at elevated temperatures; for R = Ph(PPh)6 is also formed. The thermodynamic data of the reactions 3/5 (PMe)5 ⇌ (PMe)3 and 4/5 (PMe)5 ⇌ (PMe)4 have been calculated from the equilibrium constants between 60 and 160 °C. The ring strain of 2 is much smaller than that of cyclopropane but increases with increasing size and bulk of the substituents R at the phosphorus threemembered ring.

The sorption of krypton and xenon in zeolites at high pressures and temperatures I. Chabazite

1972 ◽  
Vol 326 (1566) ◽  
pp. 315-330 ◽  
Keyword(s):  
Gas Phase ◽  
Thermodynamic Equilibrium ◽  
High Pressures ◽  
Equilibrium Constants ◽  
Standard State ◽  
Temperature Range ◽  
Thermodynamic Relationship ◽  
High Pressures And Temperatures

Isotherms of Kr and Xe in chabazite have been obtained for absolute sorption and for Gibbs excess sorption, in the temperature range 150 to 450 °C and at pressures up to 100 atm. Thermodynamic equilibrium constants for distribution of gas between the crystals and the gas phase, standard state concentrations and heats of sorption have been determined. At the highest pressures differences between absolute sorption and Gibbs excess sorption were large. The change of equilibrium fugacity with temperature for given absolute and Gibbs excess sorptions yielded two differential heats of sorption and two differential entropies of the sorbate. These heats, and the corresponding entropies, differed numerically and in their dependence upon amount sorbed. The thermodynamic relationship between the two heats has been derived and discussed.

THE DISSOCIATION OF α- AND β-LIPOVITELLIN IN AQUEOUS SOLUTION: PART I. EFFECT OF pH, TEMPERATURE, AND OTHER FACTORS

1962 ◽  
Vol 40 (3) ◽  
pp. 363-372 ◽  
Author(s):  
R. W. Burley ◽  
W. H. Cook
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Aqueous Solutions ◽  
Thermodynamic Data ◽  
Equilibrium Constants ◽  
Effect Of Ph ◽  
Reversible Dissociation ◽  
Lipoprotein Concentration ◽  
Irreversible Aggregation ◽  
Increasing Temperature

The effect of pH, temperature, ionic strength, and lipoprotein concentration on the reversible dissociation of α- and β-lipovitellin in aqueous solutions above pH 6 has been examined by ultracentrifugal measurements. Under otherwise similar conditions α- and β-lipovitellin are 50% dissociated at pH 10.5 and 7.8, respectively. Both lipovitellins undergo an irreversible aggregation above about pH 11; β-lipovitellin is sometimes converted to a non-dissociable form upon aging. Dissociation of both lipovitellins decreases with increasing ionic strength and increasing temperature. Although the ultracentrifugal method has limitations, provisional equilibrium constants and thermodynamic data were obtained from it that are comparable with those obtained for certain protein systems.

scholarly journals N-Methyl-D-Glucoseimine Synthesis Reaction Thermodynamic Properties Calculation

2020 ◽  
Vol 6 (11) ◽  
pp. 40-46
Author(s):  
S. Mikhailov ◽  
R. Brovko ◽  
S. Mushinskii ◽  
M. Sulman
Keyword(s):  
Elevated Temperatures ◽  
Equilibrium Constants ◽  
Thermodynamic Calculations ◽  
Process Conditions ◽  
Reaction Conditions ◽  
Formation Reaction ◽  
Reaction Proceeds ◽  
Energy Equilibrium ◽  
Reversible Formation ◽  
Pharmaceutical Practice

The presented article is devoted to thermodynamic calculations of the N-methyl-D-glucosimine reversible formation reaction, an intermediate product for N-methyl-D-glucosamine synthesis, which is widely used in pharmaceutical practice as a ballast or counterion that improves the bioavailability of the main active substance. N-methyl-D-glucosimine is synthesized as a result of the interaction of D-glucose with methylamine in organic solvents, the reaction is reversible, and the yield of the target product depends entirely on the reaction conditions. The use of thermodynamic calculations makes it possible to evaluate the influence of the chemical process conditions on the yield of target products, which in turn contributes to a deeper understanding of the chemical reactions mechanisms. In chemical equilibrium, direct and reverse reactions proceed at equal rates, while the concentrations of products and reagents remain constant. When the reaction proceeds in a closed system, after a certain time, a state of equilibrium occurs, while the reaction does not proceed with a complete transformation of the reagents. This article presents the results of thermodynamic calculations of the reaction for the synthesis of N-methyl-D-glucosimine by the Van Kravlen – Cheremnov method. The Gibbs energy, equilibrium constants, and D-glucose conversion were calculated as activity function of reacting substances. It was shown that an increase in the temperature of the reaction mixture from 20 to 160 °C promotes an increase in the conversion of D-glucose from 3 to 32%, and therefore it is possible to recommend carrying out this reaction at elevated temperatures.

The aqueous chemistry of tellurium: critically-selected equilibrium constants for the low-molecular-weight inorganic species

2019 ◽  
Vol 16 (4) ◽  
pp. 289 ◽  
Author(s):  
Montserrat Filella ◽  
Peter M. May
Keyword(s):  
Molecular Weight ◽  
Aqueous Solutions ◽  
Thermodynamic Data ◽  
Equilibrium Constants ◽  
Computer Programs ◽  
Experimental Investigations ◽  
Low Molecular Weight ◽  
Aqueous Chemistry ◽  
Scientific Disciplines ◽  
Inorganic Species

Environmental contextEquilibrium constants are required in many scientific disciplines such as biology, medicine, engineering, and in particular chemistry. Lack of reliable equilibrium constants for tellurium has restricted our understanding of its speciation and behaviour in the environment. This study presents a reliable set of equilibrium constants for tellurium, thereby providing a more coherent basis for future experimental investigations of the geochemistry, biochemistry and toxicology of this element. AbstractRelatively little information is available in the literature regarding the speciation and solubility of tellurium in aqueous solutions. The available thermodynamic data have been critically evaluated and entered into a thermodynamic database. The Joint Expert Speciation System suite of computer programs has been used to achieve thermodynamic consistency and provide a critically-selected set of equilibrium constants that can later be used for modelling purposes.

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