Enthalpies of transfer of acetonitrile from water to aqueous methanol, ethanol and dimethylsulphoxide mixtures at 298.15K

2006 ◽  
Vol 448 (1) ◽  
pp. 37-40 ◽  
Author(s):  
G.R. Behbehani ◽  
S. Ghammamy ◽  
W.E. Waghorne
Keyword(s):  
Aqueous Methanol ◽  
Enthalpies Of Transfer

Thermodynamics of aqueous solutions of nonelectrolytes. I. Enthalpies of transfer of 1-methyl-2-pyrrolidinone from water to aqueous methanol

1974 ◽  
Vol 3 (1) ◽  
pp. 71-79 ◽  
Author(s):  
Sachio Murakami ◽  
Reiji Tanaka ◽  
Ryoichi Fujishiro
Keyword(s):  
Aqueous Solutions ◽  
Aqueous Methanol ◽  
Enthalpies Of Transfer

Solvation of Fluoride Ions. II. Enthalpies and Entropies of Transfer From Water to Aqueous Methanol

1988 ◽  
Vol 41 (12) ◽  
pp. 1971 ◽  
Author(s):  
GT Hefter ◽  
PJ Mclay
Keyword(s):  
Composition Range ◽  
Potassium Fluoride ◽  
Alkali Metal Ions ◽  
Halide Ions ◽  
Aqueous Methanol ◽  
Fluoride Ions ◽  
Solvent Interactions ◽  
Enthalpies Of Transfer ◽  
Complex Dependence ◽  
The Individual

Enthalpies of transfer of potassium fluoride from water to water-methanol mixtures over the whole composition range have been determined by calorimetry. Combination of these values with literature data has enabled calculation of the enthalpies and entropies of transfer for the individual ions through the tetraphenylarsonium tetrapbenylborate ( tatb ) assumption. The values of ΔtH°(F-) and ΔtS°(F-) show a complex dependence on solvent composition which closely parallels the dependence of the other halide ions. These effects are discussed in terms of ion-solvent and solvent-solvent interactions. The halide ions appear to be (weakly) preferentially solvated by H2O, and the alkali metal ions by MeOH.

Conversion of fructose into methyl lactate over SnO2/Al2O3 catalystin flow regime

2020 ◽  
pp. 43-47
Author(s):  
S.V. Prudius ◽  
◽  
N.L. Hes ◽  
A.M. Mylin ◽  
V.V. Brei ◽  
...  
Keyword(s):  
Flow Reactor ◽  
Practical Interest ◽  
Dimethyl Acetal ◽  
Racemic Mixture ◽  
Process Conditions ◽  
Impregnation Method ◽  
Aqueous Methanol ◽  
Methyl Lactate ◽  
Al2o3 Catalyst ◽  
Target Reaction

In recent years, numerous researchers have focused on the development of catalytic methods for processing of biomass-derived sugars into alkyl lactates, which are widely used as non-toxic solvents and are the starting material for obtaining monomeric lactide. In this work, the transformation of fructose into methyl lactate on Sn-containing catalyst in the flow reactor that may be of practical interest was studied. The supported Sn-containing catalyst was ob-tained by a simple impregnation method of granular γ-Al2O3. The catalytic ex-periments were performed in a flow reactor at temperatures of 160-190 °C and pressure of 3.0 MPa. The 1.6-9.5 wt.% fructose solutions in 80% aqueous methanol were used as a reaction mixture. It was found that addition to a reac-tion mixture of 0.03 wt.% potassium carbonate leads to the increase in selec-tivity towards methyl lactate on 15% at 100% conversion of fructose. Prod-ucts of the target reaction С6Н12О6 + 2СН3ОН = 2С4Н8О3 + 2Н2О were ana-lyzed using 13C NMR method. The following process conditions for obtaining of 65 mol% methyl lactate yield at 100% fructose conversion were found: use of 4.8 wt.% fructose solution in 80% methanol, 180 °С, 3.0 МПа and a load on catalyst 1.5 mmol C6H12O6/mlcat/h at contact time of 11 minutes. The cata-lyst productivity is 2.0 mmol C4H8O3/mlcat/h and the by-productі are 1,3-dihydroxyacetone dimethyl acetal (20%) and 5-hydroxymethylfurfural (10%). It should be noted that a racemic mixture of L- and D-methyl lactates has been obtained by conversion of D-fructose on the SnO2/Al2O3 catalyst. The SnO2/Al2O3 catalyst was found to be stable for 6 h while maintaining full fruc-tose conversion at 55–70% methyl lactate selectivity. After regeneration the catalyst completely restores the initial activity.

Analysis of Brassinosteroids in Soybean Seeds and Leaves by Liquid Chromatography-Tandem Mass Spectrometry

2017 ◽  
Vol 10 (1) ◽  
pp. 100-109
Author(s):  
Hongxia Li ◽  
Natasha Trzaskalski ◽  
R.J. Neil Emery
Keyword(s):  
Mass Spectrometry ◽  
Liquid Chromatography ◽  
Tandem Mass Spectrometry ◽  
High Performance ◽  
Soybean Seeds ◽  
Tandem Mass ◽  
Electrospray Tandem Mass Spectrometry ◽  
Aqueous Methanol ◽  
Chromatography Tandem Mass Spectrometry ◽  
Liquid Chromatography Tandem Mass

Objective:A simple and fast high performance liquid chromatography-electrospray tandem mass spectrometry (LC-ESI-MS/MS) method has been developed for the analysis of brassinosteroids (BRs) in plants without derivatization.Materials:The BRs (including castasterone, 24-epicastasterone, brassinolide and 24-epibrassinolide) have been extracted with ice cold 80% aqueous methanol solution.Method:Five different purification strategies have been tested for the purification and enrichment of BRs.Conclusion:This analytical method was sensitive, reliable, rapid and applicable to trace analysis in complex plant samples.

Solubility and Thermodynamic Transfer Functions of Cesium Dianilinetetraisothiocyanatochromate(III)

1998 ◽  
Vol 63 (3) ◽  
pp. 293-298
Author(s):  
Vladislav Holba
Keyword(s):  
Experimental Data ◽  
Isopropyl Alcohol ◽  
Transfer Functions ◽  
Butyl Alcohol ◽  
Aqueous Methanol ◽  
Gibbs Energies ◽  
Gibbs Energy Of Transfer ◽  
Energy Of Transfer ◽  
The Given ◽  
Reference Electrolyte

The solubilities of cesium dianilinetetraisothiocyanatochromate(III) in water as well as in aqueous methanol, isopropyl alcohol, tert-butyl alcohol and acetonitrile were measured as a function of temperature and solvent composition. The Gibbs energies, enthalpies and entropies of transfer of the salt from water to the given solvents have been evaluated from experimental data. The contribution of [Cr(C6H5NH2)2(NCS)4]- ion to the Gibbs energy of transfer of the investigated salt has been calculated using the tetraphenylarsonium tetraphenylborate (TATB) reference electrolyte assumption.

Kinetics and Mechanism of Decomposition of 1,3-Bis(4-methylphenyl)triazene Catalyzed with Substituted Benzoic Acids in 25% Aqueous Methanol-General or Specific Catalysis?

1994 ◽  
Vol 59 (9) ◽  
pp. 2029-2041
Author(s):  
Oldřich Pytela ◽  
Taťjana Nevěčná
Keyword(s):  
Benzoic Acids ◽  
Hammett Equation ◽  
Aqueous Methanol ◽  
Mechanism Of Decomposition ◽  
Kinetics Of Decomposition ◽  
Independent Variable ◽  
Amino Derivatives ◽  
Substituted Benzoic Acids ◽  
The Individual ◽  
Kinetics Of

The kinetics of decomposition of 1,3-bis(4-methylphenyl)triazene catalyzed with 13 substituted benzoic acids of various concentrations have been measured in 25 vol.% aqueous methanol at 25.0 °C. The rate constants observed (297 data) have be used as values of independent variable in a series of models of the catalyzed decomposition. For the catalytic particles were considered the undissociated acid, its conjugated base, and the proton in both the specific and general catalyses. Some models presumed formation of reactive or nonreactive complexes of the individual reactants. The substituent effect is described by the Hammett equation. The statistically best model in which the observed rate constant is a superposition of a term describing the dependence on proton concentration and a term describing the dependence on the product of concentrations of proton and conjugated base is valid with the presumption of complete proton transfer from the catalyst acid to substrate, which has been proved. The behaviour of 4-dimethylamino, 4-amino, and 3-amino derivatives is anomalous (lower catalytic activity as compared with benzoic acid). This supports the presumed participation of conjugated base in the title process.

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