ChemInform Abstract: STUDIES ON SOME DEHYDROGENATION REACTIONS. PART II. DEHYDROGENATION OF 2,3-DIMETHYLBUTANE AND 1-HEXENE

1978 ◽  
Vol 9 (44) ◽  
Author(s):  
F. M. EBEID ◽  
T. I. RIHAN ◽  
R. M. HABIB ◽  
Y. BARAKA
Keyword(s):  
Dehydrogenation Reactions

scholarly journals Energetics of LOHC: Structure-Property Relationships from Network of Thermochemical Experiments and in Silico Methods

Hydrogen ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 101-121
Author(s):  
Sergey P. Verevkin ◽  
Vladimir N. Emel’yanenko ◽  
Riko Siewert ◽  
Aleksey A. Pimerzin
Keyword(s):  
In Silico ◽  
Quantum Chemical ◽  
Structure Property ◽  
Chemical Methods ◽  
Key Technology ◽  
Structure Property Relationships ◽  
Quantum Chemical Methods ◽  
Dehydrogenation Reactions ◽  
Storage Technologies ◽  
In Silico Methods

The storage of hydrogen is the key technology for a sustainable future. We developed an in silico procedure, which is based on the combination of experimental and quantum-chemical methods. This method was used to evaluate energetic parameters for hydrogenation/dehydrogenation reactions of various pyrazine derivatives as a seminal liquid organic hydrogen carriers (LOHC), that are involved in the hydrogen storage technologies. With this in silico tool, the tempo of the reliable search for suitable LOHC candidates will accelerate dramatically, leading to the design and development of efficient materials for various niche applications.

scholarly journals Electrolyte-Assisted Hydrogen Cycling in Lithium and Sodium Alanates at Low Pressures and Temperatures

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5868
Author(s):  
Jason Graetz ◽  
John J. Vajo
Keyword(s):  
Growth Parameters ◽  
Reaction Times ◽  
Hydrogen Uptake ◽  
Hydrogen Desorption ◽  
Reaction Rates ◽  
Rate Coefficients ◽  
Aluminum Hydrides ◽  
Dehydrogenation Reactions ◽  
Low Pressures ◽  
Sodium Alanates

An investigation of electrolyte-assisted hydrogen storage reactions in complex aluminum hydrides (LiAlH4 and NaAlH4) reveals significantly reduced reaction times for hydrogen desorption and uptake in the presence of an electrolyte. LiAlH4 evolves ~7.8 wt% H2 over ~3 h in the presence of a Li-KBH4 eutectic at 130 °C compared to ~25 h for the same material without the electrolyte. Similarly, NaAlH4 exhibits 4.8 wt% H2 evolution over ~4 h in the presence of a diglyme electrolyte at 150 °C compared to 4.4 wt% in ~15 h for the same material without the electrolyte. These reduced reaction times are composed of two effects, an increase in reaction rates and a change in the reaction kinetics. While typical solid state dehydrogenation reactions exhibit kinetics with rates that continuously decrease with the extent of reaction, we find that the addition of an electrolyte results in rates that are relatively constant over the full desorption window. Fitting the kinetics to an Avrami-Erofe’ev model supports these observations. The desorption rate coefficients increase in the presence of an electrolyte, suggesting an increase in the velocities of the reactant-product interfaces. In addition, including an electrolyte increases the growth parameters, primarily for the second desorption steps, resulting in the observed relatively constant reaction rates. Similar effects occur upon hydrogen uptake in NaH/Al where the presence of an electrolyte enables hydrogenation under more practical low temperature (75 °C) and pressure (50 bar H2) conditions.

17-Oxidoreduction of 17β-Estradiol, Estrone and Their 3-Sulfates by Kidney Slices from Guinea Pig and Human

1975 ◽  
Vol 53 (12) ◽  
pp. 1333-1336 ◽  
Author(s):  
R. Hobkirk ◽  
Mona Nilsen ◽  
Barbara Jennings
Keyword(s):  
Guinea Pig ◽  
Marked Reduction ◽  
Human Kidney ◽  
Kidney Cortex ◽  
Limited Extent ◽  
Tissue Slices ◽  
Ample Evidence ◽  
Sulfatase Activity ◽  
17Β Estradiol ◽  
Dehydrogenation Reactions

Slices of whole kidney and kidney cortex from the female guinea pig catalyzed a marked reduction of estrone 3-sulfate (E13S) and estrone (E1) to 17β-estradiol 3-sulfate (E23S) and 17β-estradiol (E2), respectively, as well as the reverse (dehydrogenation) reactions. Slices of medulla did not appear active in E23S–E13S interconversion but did possess the ability to interconvert E2 and E1, besides possessing considerable sulfatase activity. The use of [3H-35S]E13S and [3H-35S]E23S as substrates, together with a demonstrated lack of estrogen sulfate synthesis by the tissue slices, provided ample evidence that the intact sulfates were involved in direct oxidoreduction. Slices of human kidney cortex catalyzed the reduction of E13S to a very limited extent. Slices of whole kidney and of cortex from guinea pig formed small amounts of estrogen glucuronide(s).

scholarly journals Beyond the Woodward-Hoffman Rules: What Controls Reactivity in Eliminative Aromatic Ring-Forming Reactions?

2018 ◽  
Vol 71 (4) ◽  
pp. 249 ◽  
Author(s):  
A. D. Dinga Wonanke ◽  
Deborah L. Crittenden
Keyword(s):  
Molecular Wires ◽  
Chemical Diversity ◽  
Semiconducting Polymers ◽  
Cyclization Reactions ◽  
Rate Determining Step ◽  
Oxidation Potentials ◽  
Optimal Balance ◽  
Ring Oxidation ◽  
Dehydrogenation Reactions ◽  
Key Aspects

The Mallory (photocyclization) and Scholl (thermal cyclohydrogenation) reactions are widely used in the synthesis of extended conjugated π systems of high scientific interest and technological importance, including molecular wires, semiconducting polymers, and nanographenes. While simple electrocyclization reactions obey the Woodward-Hoffman rules, no such simple, general, and powerful model is available for eliminative cyclization reactions due to their increased mechanistic complexity. In this work, detailed mechanistic investigations of prototypical reactions reveal that there is no single rate-determining step for thermal oxidative dehydrogenation reactions, but they are very sensitive to the presence and distribution of heteroatoms around the photocyclizing ring system. Key aspects of reactivity are correlated to the constituent ring oxidation potentials. For photocyclization reactions, planarization occurs readily and/or spontaneously following photo-excitation, and is promoted by heteroatoms within 5-membered ring adjacent to the photocyclizing site. Oxidative photocyclization requires intersystem crossing to proceed to products, while reactants configured to undergo purely eliminative photocyclization could proceed to products entirely in the excited state. Overall, oxidative photocyclization seems to strike the optimal balance between synthetic convenience (ease of preparation of reactants, mild conditions, tolerant to chemical diversity in reactants) and favourable kinetic and thermodynamic properties.

scholarly journals Generic approach to access barriers in dehydrogenation reactions

2018 ◽  
Vol 1 (1) ◽  
Author(s):  
Liang Yu ◽  
Laia Vilella ◽  
Frank Abild-Pedersen
Keyword(s):  
Access Barriers ◽  
Dehydrogenation Reactions

A Magnetically Ordered Non-Stoichiometric Zinc Ferrite for the Oxidative Dehydrogenation Reactions.

2001 ◽  
Vol 676 ◽  
Author(s):  
J. A. Toledo ◽  
N. Nava ◽  
X. C. Sun ◽  
X. Bokhimi
Keyword(s):  
Catalytic Activity ◽  
Oxidative Dehydrogenation ◽  
Spinel Structure ◽  
Zinc Ferrite ◽  
Room Temperature ◽  
Annealing Temperature ◽  
Octahedral Sites ◽  
Tetrahedral Sites ◽  
Dehydrogenation Reactions ◽  
Hydrothermal Reduction

ABSTRACTZnFe2O4 nanoparticles were prepared by hydrothermal reduction approach. A considerable amount of α-Fe2O3 was segregated in the as-synthesized sample, which diffused into the tetrahedral and octahedral sites of the ZnFe2O4 spinel structure with increasing the annealing temperature. The introduction of Fe3+ into the tetrahedral positions was observed by Mössbauer spectra. Magnetization measurements showed an unusual ferrimagnetic behavior of the ZnFe2O4 phase, even at room temperature, confirming the introduction of Fe3+ into the tetrahedral sites of the spinel structure. Catalytic activity measured in the oxidative dehydrogenation of 1-butene reaction increased with increasing annealing temperature, indicating that those interactions of Fe3+ in tetrahedral and octahedral positions also promotes the activity and selectivity to butadiene formation.

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