Enthalpies of transfer of tetrabutylammonium bromide as indicators of the structure of aqueous solvents: aqueous methanol, ethanol, propan-1-ol, 2-methylpropan-2-ol and 1,4-dioxane systems

1991 ◽  
Vol 87 (1) ◽  
pp. 87 ◽  
Author(s):  
David Feakins ◽  
James Mullally ◽  
W. Earle Waghorne
Keyword(s):  
Tetrabutylammonium Bromide ◽  
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.

Sign in / Sign up

Export Citation Format

Share Document