Hydrogen transfer versus olefins methylation: On the formation trend of propene in the methanol-to-hydrocarbons reaction over Beta zeolites

Although it is recognized that niacin (pyridine-3-carboxylic acid), incorporated as the amide in nicotinamide adenine dinucleotide (NAD) or in nicotinamide adenine dinucleotide phosphate (NADP), is a cofactor in hydrogen transfer in numerous enzyme reactions in all organisms studied, virtually no information is available on the effect of this vitamin on a cell at the submicroscopic level. Since mitochondria act as sites for many hydrogen transfer processes, the possible response of mitochondria to niacin treatment is, therefore, of critical interest.Onion bulbs were placed on vials filled with double distilled water in the dark at 25°C. After two days the bulbs and newly developed root system were transferred to vials containing 0.1% niacin. Root tips were collected at ¼, ½, 1, 2, 4, and 8 hr. intervals after treatment. The tissues were fixed in glutaraldehyde-OsO4 as well as in 2% KMnO4 according to standard procedures. In both cases, the tissues were dehydrated in an acetone series and embedded in Reynolds' lead citrate for 3-10 minutes.

Download Full-text

Cobalt/Lewis Acid Catalysis for Hydrocarbofunctionalization of Alkynes via Cooperative C–H Activation

10.26434/chemrxiv.11760519.v1 ◽

2020 ◽

Author(s):

Chang-Sheng Wang ◽

Sabrina Monaco ◽

Anh Ngoc Thai ◽

Md. Shafiqur Rahman ◽

Chen Wang ◽

...

Keyword(s):

Catalytic System ◽

Lewis Acid ◽

Hydrogen Transfer ◽

Acid Catalysis ◽

Rate Limiting Step ◽

Site Selectivity ◽

Set Up ◽

Site Selective ◽

First Time ◽

Rate Limiting

A catalytic system comprised of a cobalt-diphosphine complex and a Lewis acid (LA) such as AlMe3 has been found to promote hydrocarbofunctionalization reactions of alkynes with Lewis basic and electron-deficient substrates such as formamides, pyridones, pyridines, and azole derivatives through site-selective C-H activation. Compared with known Ni/LA catalytic system for analogous transformations, the present catalytic system not only feature convenient set up using inexpensive and bench-stable precatalyst and ligand such as Co(acac)3 and 1,3-bis(diphenylphosphino)propane (dppp), but also display distinct site-selectivity toward C-H activation of pyridone and pyridine derivatives. In particular, a completely C4-selective alkenylation of pyridine has been achieved for the first time. Mechanistic stidies including DFT calculations on the Co/Al-catalyzed addition of formamide to alkyne have suggested that the reaction involves cleavage of the carbamoyl C-H bond as the rate-limiting step, which proceeds through a ligand-to-ligand hydrogen transfer (LLHT) mechanism leading to an alkyl(carbamoyl)cobalt intermediate.

Download Full-text

Nanometer Scale Spectroscopic Visualization of Catalytic Sites During a Hydrogenation Reaction on a Pd/Au Bimetallic Catalyst

10.26434/chemrxiv.12346823.v3 ◽

2020 ◽

Author(s):

hao yin ◽

Liqing Zheng ◽

Wei Fang ◽

Yin-Hung Lai ◽

Nikolaus Porenta ◽

...

Keyword(s):

Catalytic Hydrogenation ◽

Density Functional ◽

Hydrogen Transfer ◽

Bimetallic Catalyst ◽

Local Environment ◽

Hydrogenation Reaction ◽

Boundary Density ◽

Catalytic Sites ◽

Powerful Analytical Tool ◽

Tip Enhanced Raman Spectroscopy

Understanding the mechanism of catalytic hydrogenation at the local environment requires chemical and topographic information involving catalytic sites, active hydrogen species and their spatial distribution. Here, tip-enhanced Raman spectroscopy (TERS) was employed to study the catalytic hydrogenation of chloro-nitrobenzenethiol on a well-defined Pd(sub-monolayer)/Au(111) bimetallic catalyst (pH2=1.5 bar, 298 K), where the surface topography and chemical fingerprint information were simultaneously mapped with nanoscale resolution (≈10 nm). TERS imaging of the surface after catalytic hydrogenation confirms that the reaction occurs beyond the location of Pd sites. The results demonstrate that hydrogen spillover accelerates hydrogenation at the Au sites within 20 nm from the bimetallic Pd/Au boundary. Density functional theory was used to elucidate the thermodynamics of interfacial hydrogen transfer. We demonstrate that TERS as a powerful analytical tool provides a unique approach to spatially investigate the local structure-reactivity relationship in catalysis.

Download Full-text

Nanometer Scale Spectroscopic Visualization of Catalytic Sites During a Hydrogenation Reaction on a Pd/Au Bimetallic Catalyst

10.26434/chemrxiv.12346823.v1 ◽

2020 ◽

Author(s):

Hao Yin ◽

Liqing Zheng ◽

Wei Fang ◽

Yin-Hung Lai ◽

Nikolaus Porenta ◽

...

Keyword(s):

Catalytic Hydrogenation ◽

Density Functional ◽

Hydrogen Transfer ◽

Bimetallic Catalyst ◽

Local Environment ◽

Hydrogenation Reaction ◽

Boundary Density ◽

Catalytic Sites ◽

Powerful Analytical Tool ◽

Tip Enhanced Raman Spectroscopy

Understanding the mechanism of catalytic hydrogenation at the local environment requires chemical and topographic information involving catalytic sites, active hydrogen species and their spatial distribution. Here, tip-enhanced Raman spectroscopy (TERS) was employed to study the catalytic hydrogenation of chloro-nitrobenzenethiol on a well-defined Pd(sub-monolayer)/Au(111) bimetallic catalyst (pH2=1.5 bar, 298 K), where the surface topography and chemical fingerprint information were simultaneously mapped with nanoscale resolution (≈10 nm). TERS imaging of the surface after catalytic hydrogenation confirms that the reaction occurs beyond the location of Pd sites. The results demonstrate that hydrogen spillover accelerates hydrogenation at the Au sites within 20 nm from the bimetallic Pd/Au boundary. Density functional theory was used to elucidate the thermodynamics of interfacial hydrogen transfer. We demonstrate that TERS as a powerful analytical tool provides a unique approach to spatially investigate the local structure-reactivity relationship in catalysis.

Download Full-text

Rapid, Non-Toxic Synthesis of Beta Zeolites

10.26434/chemrxiv.6432155 ◽

2018 ◽

Author(s):

Felix Hemmann ◽

Jonathan Hackebeil ◽

Andreas Lißner ◽

Florian Mertens

Keyword(s):

Hydrofluoric Acid ◽

Molecular Sieves ◽

Toxic Chemicals ◽

Lewis Acidity ◽

Beta Zeolite ◽

Seeded Growth ◽

Related Research ◽

Beta Zeolites ◽

Growth Method ◽

Fast Synthesis

Molecular sieves with beta zeolite topology are promising catalysts for various reactions as they exhibits extraordinary Lewis acidity. However, their industrial application and related research in academica is hindered because their synthesis is time consuming and typically involves toxic chemicals as hydrofluoric acid. Therefore, tetraethylammonium fluorid was tested as a non-toxic fluotide source for the synthesis of beta zeolites. In combination with the previously reported nano-seeded growth method, a fast synthesis of beta zeolites only involving non-toxic chemicals was possible. Synthesized zeolites show comparable selectivity in the Bayer-Villinger oxidation as conventional zeolites synthesized with hydrofluoric acid.

Download Full-text

A Facile One-pot Synthesis of Substituted Quinolines via Cascade Friedlander Reaction from Isoxazoles with Ammonium Formate-Pd/C and Ketones

Letters in Organic Chemistry ◽

10.2174/1570178616666190618091617 ◽

2020 ◽

Vol 17 (3) ◽

pp. 211-215

Author(s):

Da Chen ◽

Xuan Wang ◽

Runnan Wang ◽

Yao Zhan ◽

Xiaohan Peng ◽

...

Keyword(s):

Hydrogen Transfer ◽

Ammonium Formate ◽

Aromatic Ketone ◽

Reaction Conditions ◽

One Pot ◽

Diverse Range ◽

Strong Base ◽

Aromatic Ketones ◽

Substituted Quinolines ◽

New Strategy

The Friedlander reaction is the most commonly used method to synthesis substituted quinolines, the essential intermediates in the medicine industry. A facile one-pot approach for synthesizing substituted quinolines by the reaction of isoxazoles, ammonium formate-Pd/C, concentrated sulfuric acid, methanol and ketones using Friedlander reaction conditions is reported. Procedures for the synthesis of quinoline derivatives were optimized, and the yield was up to 90.4%. The yield of aromatic ketones bearing electron-withdrawing groups was better than the ones with electron-donating substituents. The structures of eight substituted quinolines were characterized by MS, IR, H-NMR and 13CNMR, which were in agreement with the expected structures. The mechanism for the conversion was proposed, which involved the Pd/C catalytic hydrogen transfer reduction of unsaturated five-membered ring of isoxazole to produce ortho-amino aromatic ketones. Then the nucleophilic addition of with carbonyl of the ketones generated Schiff base in situ, which underwent an intermolecular aldol reaction followed by the elimination of H2O to give production of substituted quinolines. This new strategy can be readily applied for the construction of quinolines utilizing a diverse range of ketones and avoids the post-reaction separation of the o-amino aromatic ketone compounds. The conventionally used o-amino aromatic ketone compounds in Friedlander reaction to prepare substituted quinoline are laborious to synthesize and are apt to self-polymerize. While oxazole adopted in this work can be prepared at ease by the condensation of benzoacetonitrile and nitrobenzene derivatives under the catalysis of a strong base. Moreover, the key features of this protocol are readily available starting materials, excellent functional group tolerance, mild reaction conditions, operational simplicity, and feasibility for scaling up.

Download Full-text

Intermolecular hydrogen transfer in unsaturated hydrocarbons induced by dimeric titanocene

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19832924 ◽

1983 ◽

Vol 48 (10) ◽

pp. 2924-2936 ◽

Cited By ~ 5

Author(s):

Karel Mach ◽

Lidmila Petrusová ◽

Helena Antropiusová ◽

Vladimír Hanuš ◽

František Tureček ◽

...

Keyword(s):

Hydrogen Transfer ◽

Titanium Content ◽

Esr Spectra ◽

Stable Complex ◽

Catalytic Complex ◽

Substitution Reactions ◽

Unsaturated Hydrocarbons ◽

Linear Alkanes ◽

Saturated And Aromatic Hydrocarbons ◽

Intermolecular Hydrogen Transfer

μ-(η5 : η5-Fulvalene)-di-μ-hydrido-bis(η5-cyclopentadienyltitanium) and μ-(η5 : η5-fulvalene)-μ-chloro-μ-hydrido-bis(cyclopentadienyltitanium) form a thermally stable complex which catalyzes the intermolecular hydrogen transfer in unsaturated hydrocarbons, in addition to isomerizations and cyclizations. Cyclic hydrocarbons disproportionate under catalysis to saturated and aromatic hydrocarbons, while linear olefins yield predominantly linear alkanes and high molecular weight tar. The catalyst enables the hydrocarbon system to approach the thermodynamic equilibrium through a series of substitution reactions between alkyl- and allyltitanocene-like species and olefins and dienes. The catalytic complex was characterized by UV and ESR spectra. About one half of overall titanium content could be converted to mononuclear η3-allyltitanocene-like species, stable up to 400 °C. This exceptional thermal stability is ascribed to a firmly bound allyl containing ligand.

Download Full-text

Transformation of methanol to hydrocarbons over Y zeolites with varying Si/Al ratio

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19871701 ◽

1987 ◽

Vol 52 (7) ◽

pp. 1701-1707 ◽

Cited By ~ 1

Author(s):

Miloslav Křivánek ◽

Nguyen Thiet Dung ◽

Pavel Jírů

Keyword(s):

Catalytic Activity ◽

Reaction Time ◽

Coke Formation ◽

Aliphatic Hydrocarbons ◽

Y Zeolite ◽

Y Zeolites ◽

Methanol To Hydrocarbons

The catalytic activity of Na, H-Y zeolite samples with a varying Si/Al ratio (2·5 to 20) in the transformation of methanol was determined. The amounts of formed individual aliphatic hydrocarbons as function of reaction time were correlated with the amount of Bronsted and Lewis centres on the catalysts. The effect of coke formation on the over-all course of the reaction has been demonstrated.

Download Full-text