scholarly journals Uranyl-catalyzed C-H Alkynylation and Olefination

2021 ◽  
Author(s):  
Yu Mao ◽  
Yeqing Liu ◽  
Lei Yu ◽  
Shengyang Ni ◽  
Yi Wang ◽  
...  
Keyword(s):  
Crystallographic Analysis ◽  
Oxidizing Agent ◽  
Peroxo Complexes ◽  
Hydrogen Atoms ◽  
Uranyl Cation

Abstract Uranyl cation (UO22+) has been identified as highly oxidizing agent to abstract hydrogen atoms from C-H bonds for the formation of carbon-centered radicals. This work described a photocatalytic strategy to utilize uranyl peroxo complexes for direct alkynylation and olefination of C(sp3) aliphatics. Crystallographic analysis revealed that the in situ generated uranyl peroxide accelerated the reaction.

Uranyl-catalysed C-H Alkynylation and Olefination

2021 ◽  
Author(s):  
Yu Mao ◽  
Yeqing Liu ◽  
Lei Yu ◽  
Shengyang Ni ◽  
Yi Wang ◽  
...  
Keyword(s):  
Oxidizing Agent ◽  
Hydrogen Atoms ◽  
Uranyl Cation

This work describes a strategy to utilise uranyl for direct alkynylation and olefination of amides. Uranyl cation (UO22+) has been identified as highly oxidizing agent to abstract hydrogen atoms from...

In-situ low temperature cleaning of silicon surfaces using hydrogen atoms

Vacuum ◽  
1995 ◽  
Vol 46 (7) ◽  
pp. 667-672 ◽  
Author(s):  
A Crossley ◽  
C.J. Sofield ◽  
S Sugden ◽  
R Clampitt ◽  
C Bradley
Keyword(s):  
Low Temperature ◽  
Silicon Surfaces ◽  
Hydrogen Atoms

Studies on the thermal coking of bitumen. I. The use of pyrene-d10 as a probe for evaluating the extent of hydrogen shuttling reaction

1991 ◽  
Vol 69 (1) ◽  
pp. 116-120 ◽  
Author(s):  
M. J. Kirk ◽  
T. S. Sorensen
Keyword(s):  
Free Radicals ◽  
Key Words ◽  
Hydrogen Exchange ◽  
Solvent Free ◽  
Hydrogen Donor ◽  
Organic Reactions ◽  
Hydrogen Atoms ◽  
Donor Solvent ◽  
Key Words Bitumen

The organic reactions that take place during the thermal coking of bitumen are extremely complex and deep-seated, but obviously hydrogen atoms originally attached to carbons that form coke will have moved to a new carbon site (net addition of hydrogen, resulting in upgraded bitumen). Accompanying this process, one expects some general hydrogen shuttling between non-coking molecules. This paper describes an approach to determing the extent of this latter process by the addition of a small amount of perdeuterated pyrene to the bitumen prior to the coking operation. The in situ pyrene functions as in indicator, allowing one to establish the extent and other mechanistic details of the "hydrogen donor" reactions that take place during coking. There is no indication that the pyrene substantially modifies the normal course of the reaction, hence the analogy to an indicator. Key words: bitumen coking, pyrene, hydrogen exchange, donor solvent, free radicals.

scholarly journals 10H-Pyrazino[2,3-b][1,4]benzotellurazine, a Novel Tellurium-Containing Heterocyclic System

2020 ◽  
Vol 2020 ◽  
pp. 1-5
Author(s):  
Diamond S. Smith ◽  
Dallas N. Alexis ◽  
Frank R. Fronczek ◽  
Thomas Junk
Keyword(s):  
Title Compound ◽  
Heterocyclic System ◽  
Crystallographic Analysis ◽  
Supramolecular Assemblies ◽  
Methyl Derivative ◽  
X Ray ◽  
Hydrogen Bonded

Condensation of 2,3-dichloropyrazine with 2-aminobenzenetellurole and 2-amino-5-methylbenzenetellurole, generated in situ by reduction of the corresponding ditellurides, resulted in the formation of novel 10H-pyrazino[2,3-b][1,4]benzotellurazine and its 7-methyl derivative. The products were purified via their well-crystallized 5,5-dibromo derivatives. X-ray crystallographic analysis of the title compound indicates that it has a pronounced V-shape and forms hydrogen-bonded dimers. Te, N-containing heterocycles have the potential of offering access to supramolecular assemblies.

scholarly journals CO2-induced single-crystal to single-crystal transformations of an interpenetrated flexible MOF explained by in situ crystallographic analysis and molecular modeling

2019 ◽  
Vol 10 (43) ◽  
pp. 10018-10024 ◽  
Author(s):  
Arpan Hazra ◽  
Dewald P. van Heerden ◽  
Somananda Sanyal ◽  
Prem Lama ◽  
Catharine Esterhuysen ◽  
...  
Keyword(s):  
Molecular Modeling ◽  
Single Crystal ◽  
Intermediate Phase ◽  
Crystallographic Analysis ◽  
Detailed Explanation ◽  
Large Pore

A flexible twofold interpenetrated MOF reversibly switches between closed, narrow and large pore forms. In situ crystallographic analysis of a narrow-pore intermediate phase provides a detailed explanation of a plateau observed during desorption.

Hypervalent Molecular Cluster: C28H4

2005 ◽  
Vol 494 ◽  
pp. 181-186
Author(s):  
M. Veljković ◽  
O. Nešković ◽  
A. Djerić ◽  
S. Veličković ◽  
V. Šipka
Keyword(s):  
Mass Spectrometry ◽  
Mass Spectrometer ◽  
Source Parameters ◽  
Carbon Cluster ◽  
Ion Source ◽  
Molecular Cluster ◽  
Hydrogen Atoms ◽  
Cluster Source ◽  
The Impact

A growing number of recent publications on clusters reflect a tremendous interest in these particles. These studies reveal new fundamental physical and chemical aspects of matter. Clusters are called the fifth state of matter: liquid, solid, cluster, gas and plasma. In this work, a carbon cluster was generated by a spark cluster source and detected by single focusing mass spectrometer in situ. We examined the effects of cluster source parameters on the generation of carbon cluster and report our initial results. This method should be useful for studying the mechanism of fullerene formation. In the case when carbon clusters generated in plasma arc are carried by the Ar or H2 gas flow downstream through a vacuum chamber to the ion source of mass spectrometer, we obtained a small binary carbon cluster C28H4 (hydrogenated fullerene). The empty fullerene is tetravalent and strongly binds four hydrogen atoms, which significantly weakens two different sets of bonds and leads to an open-shell electronic structure. Conclusion is that endohedral C28H4 are hypervalent. We have demonstrated how in situ mass spectrometry has led to the rapid development of an important branch of synthetic fullerene chemistry that has yielded many new small fullerenes and related derivatives with novel structures and properties. The impact of mass spectrometry on the synthesis of fullerene derivatives is the subject of this paper. Significantly, a large fraction of products could be condensed on a specially designed collection plate, which allows further spectroscopic characterization of new derivatives.

Synthesis and Microwave Characterization of Polypyrrole-PVC Blends

1992 ◽  
Vol 247 ◽  
Author(s):  
F. Jousse ◽  
P. Hourquebie ◽  
C. Deleuze ◽  
L. Olmedo
Keyword(s):  
In Situ Growth ◽  
Oxidizing Agent ◽  
Direct Link ◽  
Reaction Parameters ◽  
Solvent Nature ◽  
Microwave Characterization ◽  
Agent Control ◽  
Thermoplastic Blends

ABSTRACT.: Thermoplastic blends have been created by in situ growth of polypyrrole in an insulating PVC matrix. This type of synthesis gives a level of conductivity of the order of 10−5 to 1 S/cm for concentrations of less than 15% (in weight). A study of the synthetic conditions shows that the reaction parameters (solvent, nature of oxidizing agent) control the eventual properties of the blend (structure, conductivity level). The microwave characterization of these materials has allowed us to establish a direct link between the method of processing and the radioelectric properties.

Mineral reservoirs and behaviors of hydrogen in Earth’s lower mantle

2020 ◽  
Author(s):  
Qingyang Hu ◽  
Ho-kwang Mao
Keyword(s):  
Lower Mantle ◽  
Hydrogen Ions ◽  
Geochemical Processes ◽  
Transport Mechanisms ◽  
Hydrogen Atoms ◽  
And Behaviors ◽  
Isotopic Mixing ◽  
Laser Heated ◽  
Diffusion Of Hydrogen

<p>The incorporation of H into minerals imposes profound effects on their physicochemical signatures of the solid Earth. The locations of hydrogen reservoirs are detected by seismology. However, the mineral responsible for storing large quantity of hydrogen, particularly in Earth’s lower mantle is still controversial. Combining a set of in-situ probes at high pressure-temperature and first principles simulation, we investigated the solubility and behaviors of H in silica and hydroxide up to the conditions found at the core-mantle boundary. The solubility of hydrogen keeps high in those minerals even along the mantle geotherm. Under deep lower mantle pressures, hydrogen atoms are free from the hydroxyl bonding and becomes highly diffusive. The swift diffusion of hydrogen ions induces soaring electrical conductivity when the sample is laser heated. Those exotic properties indicate novel transport mechanisms for both charge and mass at Earth’s deep lower mantle. The potential of hydrogen enriched volatile reservoirs may carry major impacts on the electrical and magnetic behaviors, as well as redox, H isotopic mixing, and other geochemical processes in the Earth’s deep interiors.</p>

Preparation and mechanisms of cemented carbides with ultrahigh fracture strength

2015 ◽  
Vol 48 (4) ◽  
pp. 1254-1263 ◽  
Author(s):  
Xingwei Liu ◽  
Xiaoyan Song ◽  
Haibin Wang ◽  
Xuemei Liu ◽  
Xilong Wang ◽  
...  
Keyword(s):  
Particle Size ◽  
Fracture Strength ◽  
Growth Inhibitor ◽  
Mean Value ◽  
Crystallographic Analysis ◽  
Cemented Carbides ◽  
Composite Powders ◽  
Grain Growth Inhibitor ◽  
Carbon Concentrations

WC–Co cemented carbides were prepared by liquid-state sintering ofin situsynthesized composite powders with a constant Co content but different carbon concentrations, and with different size scales of VC particles as grain-growth inhibitor. With an optimized carbon addition and doping with microscale VC particles, an ultrahigh fracture strength with a mean value above 5000 MPa was achieved for cemented carbides. By detailed crystallographic analysis of the configuration and interactions of the WC, Co and VC phases, the effects of VC particle size on the microstructure and mechanical properties of cemented carbides are identified. The mechanisms by which the fracture strength depends on the VC particle size contain the effects on the changes in Co binder distribution, atomic matching at the phase boundary and WC grain size. The dominant factors for ultrahigh fracture strength of cemented carbides are proposed.

Evolution of Hydrogen Related Defects in Plasma Hydrogenated Crystalline Silicon under Thermal and Laser Annealing

2005 ◽  
Vol 108-109 ◽  
pp. 211-216
Author(s):  
Yue Ma ◽  
Yue Long Huang ◽  
Reinhart Job ◽  
Wolfgang Düngen ◽  
Wolfgang R. Fahrner
Keyword(s):  
Laser Annealing ◽  
Crystalline Silicon ◽  
Chemical Vapor ◽  
Basic Mechanism ◽  
Hydrogen Atoms ◽  
In Situ Raman Spectroscopy ◽  
In Situ Raman ◽  
First Order Kinetics ◽  
Boron Doped

Boron doped [100]-oriented Cz Si wafers are hydrogenated with a plasma enhanced chemical vapor deposition setup at a substrate temperature of about 260 °C. In-situ Raman spectroscopy is applied on samples under thermal and laser annealing. It is found that different Si-H species have different stabilities. The most stable one is the Si-H bond at the inner surfaces of the platelets. The dissociated energy of Si-H bonds is deduced based on the first order kinetics. It is found that the hydrogen atoms which are released during annealing are trapped again by the platelets and passivate the silicon dangling bonds at the inner surfaces of the platelets or form H2 molecules in the open platelet volume, possibly relating to the basic mechanism of the hydrogen-induced exfoliation of the silicon wafer and the socalled “smart-cut” process.

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