Characterization of anion solvation in N-methylacetamide. Transfer enthalpies of anions and the reaction rates of ethyl iodide with bromide ion in N-methylacetamide–acetonitrile and N-methylacetamide–N,N-dimethylacetamide mixtures

1986 ◽  
Vol 82 (7) ◽  
pp. 2141 ◽  
Author(s):  
Yasuhiko Kondo ◽  
Akikazu Nakano ◽  
Shigekazu Kusabayashi
Keyword(s):  
Reaction Rates ◽  
Ethyl Iodide ◽  
Bromide Ion

Three-Dimensional Computation of Gas Turbine Combustors and the Validation Studies of Turbulence and Combustion Models

1997 ◽  
Author(s):  
D. Biswas ◽  
K. Kawano ◽  
H. Iwasaki ◽  
M. Ishizuka ◽  
S. Yamanaka
Keyword(s):  
Gas Turbine ◽  
Validation Studies ◽  
Three Dimensional ◽  
Chemical Species ◽  
Reaction Rates ◽  
Reacting Flows ◽  
Gas Turbine Combustor ◽  
Combustion Models ◽  
Rate Of Dissipation

The main aim or the present work is to explore computational fluid dynamics and related turbulence and combustion models for application to the design, understanding and development of gas turbine combustor. Validation studies were conducted using the Semi-Implicit Method for Pressure Linked Equations (SIMPLE) scheme to solve the relevant steady, elliptical partial differential equations of the conservation of mass, momentum, energy and chemical species in three-dimensional cylindrical co-ordinate system to simulate the gas turbine combustion chamber configurations. A modified version of k-ε turbulence model was used for characterization of local turbulence in gas turbine combustor. Since, in the present study both diffusion and pre-mixed combustion were considered, in addition to familiar bi-molecular Arhenius relation, influence of turbulence on reaction rates was accounted for based on the eddy break up concept of Spalding and was assumed that the local reaction rate was proportional to the rate of dissipation of turbulent eddies. Firstly, the validity of the present approach with the turbulence and reaction models considered is checked by comparing the computed results with the standard experimental data on recirculation zone, mean axial velocity and temperature profiles, etc. for confined, reacting and non-reacting flows with reasonably well defined boundary conditions. Finally, the results of computation for practical gas turbine combustor using combined diffusion and pre-mixed combustion for different combustion conditions are discussed.

scholarly journals Characterization of Polyhalogenated 4-Methylphenol Dimers (Br/Cl-Predioxins) Formed during Aqueous Chlorination of 4-Methylphenol Solution in the Presence of Bromide Ion

2008 ◽  
Vol 54 (4) ◽  
pp. 423-431 ◽  
Author(s):  
Sukeo Onodera ◽  
Toshinari Takahashi ◽  
Shinya Takemoto ◽  
Tsunehiro Oh-i
Keyword(s):  
Bromide Ion

scholarly journals Radioisotopic Tracer Technique for Characterization of Nuclear and Non-Nuclear Grade Ion Exchange Resins Tulsion A-23 and Indion-810

2013 ◽  
Vol 11 ◽  
pp. 1-5
Author(s):  
Pravin U. Singare
Keyword(s):  
Ion Exchange ◽  
Reaction Rate ◽  
Nuclear Grade ◽  
Ion Exchange Resins ◽  
Specific Reaction Rate ◽  
Experimental Conditions ◽  
Specific Reaction ◽  
Bromide Ion ◽  
Exchange Resins

In the present paper 82Br radioactive tracer isotopes was used for characterization of nuclear and non-nuclear grade ion exchange resins Tulsion A-23 and Indion-810 respectively. The bromide ion-isotopic exchange reactions were performed by equilibrating 1.000 g of conditioned resins in bromide form with labeled bromide ion solution of different concentrations ranging from 0.001 M to 0.004 M, in the temperature range of 30.0 °C to 45.0 °C. The resins were characterized by comparing the values of specific reaction rate (min-1), amount of bromide ion exchanged (mmol) and percentage of bromide ions exchanged under identical experimental conditions. It was observed that the above values decrease with rise in temperature and increases with increase in concentration of labeled bromide ion solution. From the experimental values of specific reaction rate, amount and percentage of bromide ions exchanged, it was observed that Tulsion A-23 resins are superior to Indion-810 resins under identical experimental conditions.

scholarly journals Taming Super Lewis Acids for Catalysis: The Family of Ferrocene-Stabilized Silicon Cations

2014 ◽  
Author(s):  
Martin Oestreich ◽  
Hendrik Klare ◽  
Kristine Müther ◽  
Roland Fröhlich
Keyword(s):  
Low Temperatures ◽  
Lewis Acids ◽  
Acid Catalysis ◽  
Electron Pair ◽  
Reaction Rates ◽  
Diels Alder ◽  
Strong Electron ◽  
The Family ◽  
Electron Deficiency

Tricoordinate silicon cations are exceptionally strong electron pair acceptors, so strong that they react with almost any σ and π basic molecule. In order to use such reactive intermediates in synthetic chemistry, Lewis acid catalysis in particular, we have designed intramolecularly stabilized silylium ions whose electron deficiency is attenuated by an adjacent, electron-rich ferrocenyl fragment. Here we wish to present the synthesis and structural characterization of these unique transition metal-stabilized silicon cations which reveal an unprecedented bonding situation different from its isoelectronic analogues. The potential of this motif is further highlighted in challenging Diels–Alder reactions, which are catalyzed at low temperatures with exceptional reaction rates and selectivities.

Sustainable vanadium(V)-catalyzed oxybromination of styrene: Two-phase system versus ionic liquids

2005 ◽  
Vol 77 (9) ◽  
pp. 1575-1581 ◽  
Author(s):  
Valeria Conte ◽  
Barbara Floris ◽  
Pierluca Galloni ◽  
Adriano Silvagni
Keyword(s):  
Ionic Liquids ◽  
Aqueous Phase ◽  
Chlorinated Solvents ◽  
Reaction Rates ◽  
Point Of View ◽  
Metal Catalyst ◽  
Phase System ◽  
Two Phase ◽  
System Versus ◽  
Bromide Ion

Oxybromination reaction of styrene was performed in a two-phase system of water/ionic liquids (ILs). The aim of the work was to make the mild and efficient two-phase system previously developed for the vanadium(V)-catalyzed oxybromination of alkenes, inspired by the activity of haloperoxidase enzymes, even more interesting from a sustainable point of view. As in that case, a brominating intermediate was formed from the metal catalyst, H2O2, and bromide ion in the acid aqueous phase, but chlorinated solvents were replaced with ILs.[bmim+][PF6-], [bm2im+][PF6-], [bmim+][BF4-], [bmim+][CF3SO3-], and [bmim+][(CF3SO2)2N-] were tested. We report on interesting results in terms of reaction rates and selectivities.

scholarly journals Radiotracer Technique in Study of Strongly Basic Anion Exchange Resins Dowex-SBR LC and Indion-454

2013 ◽  
Vol 18 ◽  
pp. 37-49
Author(s):  
P.U. Singare
Keyword(s):  
Ion Exchange ◽  
Exchange Reaction ◽  
Anion Exchange ◽  
Isotopic Exchange ◽  
Ion Exchange Resins ◽  
Anion Exchange Resins ◽  
Isotopic Exchange Reaction ◽  
Bromide Ion ◽  
Exchange Resins

The present paper demonstrates application of isotopic tracer technique in characterization of anion exchange resins Dowex-SBR LC and Indion-454 for which 131I and 82Br radio isotopes were used. The characterization was made based on iodide and bromide ion-isotopic exchange reaction kinetic data obtained for the two resins. It was observed that during iodide ion-isotopic exchange reaction performed at 35.0 °C, 1.000 g of ion exchange resins and 0.002 mol/L labeled iodide ion solution, the values of specific reaction rate (min-1), amount of ion exchanged (mmol), initial rate of ion exchange (mmol/min) and log Kd were 0.379, 0.426, 0.161 and 16.2 respectively for Dowex-SBR LC resin, which was higher than the respective values of 0.156, 0.243, 0.038 and 13.4 as that obtained by using Indion-454 resins. The identical trend was observed for the two resins during bromide ion-isotopic exchange reaction. The results of present investigation also indicate that during the two ion-isotopic exchange reactions, for both the resins, there exists a strong positive linear correlation between amount of ions exchanged and concentration of ionic solution; and strong negative correlation between amount of ions exchanged and temperature of exchanging medium. Based on overall results it appears that under identical experimental conditions, as compared to Indion-454 resins, Dowex-SBR LC resins show superior performance. It is expected here that the present technique can be extended further for characterization of different ion exchange resins which will further help in the selection of those reins for the specific industrial application

scholarly journals Mechanistic Insight from Full Quantum Mechanical Modeling: Laccase as a Detoxifier of Aflatoxins

2021 ◽  
Author(s):  
Marco Zaccaria ◽  
William Dawson ◽  
Darius Russell Kish ◽  
Massimo Reverberi ◽  
Maria Carmela Bonaccorsi di Patti ◽  
...  
Keyword(s):  
Density Functional ◽  
Reaction Rates ◽  
Enzyme Engineering ◽  
Amino Acid Residues ◽  
Structural Elements ◽  
Mechanical Modeling ◽  
Functional Theory ◽  
Full Quantum

AbstractWe demonstrate a path towards full Quantum Mechanics (QM) characterization of enzymatic activity. As a case-study, we investigate the detoxification of aflatoxin, a carcinogenic food contaminant, by laccase, a versatile oxidase capable of—but not efficient for—degrading aflatoxin. We use a combination of quantitative experimentation and QM modeling to show that low enzymatic steric affinity for aflatoxin is the main bottleneck, rather that the oxidative activity of laccase. To identify the structural elements responsible for low reaction rates, we perform a density functional theory (DFT) based modeling of both the substrate and the enzyme in a full QM simulation of more than 7,000 atoms. Thanks to our approach we point to amino acid residues that determine the affinity of laccase for aflatoxin. We show that these residues are substrate-dependent, making a full QM approach necessary for enzyme optimization. Altogether, we establish a roadmap for rational enzyme engineering applicable beyond our case study.

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