Thermal rearrangement of optically active tetradeuterated 2-methoxymethyl-methylenecyclopropane and the bent bond/antiperiplanar hypothesis

2019 ◽  
Vol 17 (29) ◽  
pp. 7007-7012 ◽  
Author(s):  
Ghislain Deslongchamps ◽  
Pierre Deslongchamps
Keyword(s):  
Mechanistic Model ◽  
Optically Active ◽  
Thermal Rearrangement ◽  
First Time

The bent bond/antiperiplanar hypothesis (BBAH) provides, for the first time, a mechanistic model that rationalizes methylenecyclopropane rearrangements.

Bifunctional squaramide catalyzed stereoselective Mannich reaction of α-azido ketones with isatin-derived ketimines

2020 ◽  
Vol 18 (3) ◽  
pp. 479-487 ◽  
Author(s):  
Seda Karahan ◽  
Cihangir Tanyeli
Keyword(s):  
Mannich Reaction ◽  
Optically Active ◽  
First Time ◽  
High Stereoselectivity

Bifunctional squaramide catalyzed asymmetric Mannich reaction of alpha-azido ketones and isatin derived ketiminines were established for the first time with high stereoselectivity. Adducts are valuable synthons for optically active heterocycles.

Effect of PTFE on Thermal Conductivity of Gas Diffusion Layers of PEM Fuel Cells

2013 ◽  
Author(s):  
Hamidreza Sadeghifar ◽  
Ned Djilali ◽  
Majid Bahrami
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Contact Resistance ◽  
Performance Modeling ◽  
Mechanistic Model ◽  
Pem Fuel Cells ◽  
Gas Diffusion ◽  
Gas Diffusion Layers ◽  
Diffusion Layers ◽  
First Time

Through-plane thermal conductivity of 14 SIGRACET gas diffusion layers (GDLs), including series 24 & 34, as well as 25 & 35, are measured under different compressive pressures, ranging from 2 to 14 bar, at the temperature of around 60 °C. The effect of compression, PTFE loadings, and micro porous layer (MPL) on thermal conductivity of the GDLs and their contact resistance with an iron clamping surface is experimentally investigated. The contact resistance of MPL coated on GDL with the substrate of that GDL is measured for the first time in this paper. A new robust mechanistic model is presented for predicting the through-plane thermal conductivity of GDLs treated with PTFE and is successfully verified with the present experimental data. The model can predict the experimentally-observed reduction in thermal conductivity as a result of PTFE treatment and provides detailed insights on performance modeling of PEMFCs.

Thermal rearrangement of optically active α-hydroxy-imines to α-amino-ketones

1967 ◽  
Vol 0 (20) ◽  
pp. 1058-1060
Author(s):  
Shun-ichi Yamada ◽  
Hatsuhiko Mizuno ◽  
Shiro Terashima
Keyword(s):  
Optically Active ◽  
Thermal Rearrangement

An Investigation of Morphology Dependent Charge Storage in Polypyrrole Membranes

2014 ◽  
Author(s):  
Robert G. Northcutt ◽  
John M. Thornton ◽  
Vishnu Baba Sundaresan
Keyword(s):  
Specific Capacitance ◽  
Mechanistic Model ◽  
Morphological Properties ◽  
Polymer Backbone ◽  
Polymer Interface ◽  
Redox Sites ◽  
Reversible Redox ◽  
Ion Storage ◽  
First Time ◽  
Super Capacitors

PPy-based membranes exchange ions with electrolyte through reversible redox processes and hence are best suited as electrodes for batteries and super capacitors. The energy density of batteries and super capacitors are dependent on the specific capacitance of the conducting polymer and can be represented through a mechanistic model for ion transport. Through this model, the specific capacitance of polypyrrole-based membranes is shown to be dependent on the number of accessible redox sites at the electrolyte-polymer interface. The accessibility of redox sites at the electrolyte-polymer interface can be increased by controlling the morphological properties and distribution of dopant in the polymer backbone. Thus, by nanostructuring and by controlling the distribution of the dopant in the polymer, we have shown that the capacitance of PPy-based membranes can be increased to 490 F.g−1 for a 50 mV.sec−1 scan rate and 0.6 g.cm−2 specific mass. Despite this value of specific capacitance being the highest reported for PPy-based membranes to date, it is estimated that only 69% of active redox sites are used for ion storage and hence can be increased further. Maximizing specific capacitance requires an understanding of spatial distribution of redox sites in the polymer backbone and its corresponding chemoelectrical activity. In order to generate a spatial map of ion storage in PPy-based membranes, this article presents for the first time a shear-force (SF) based topography imaging and scanning electrochemical microscopy (SECM) imaging of the PPy(DBS) under reduced and oxidized conditions. From a correlated topography and chemoelectrical activity of PPy-based membrane, the data shows the availability of redox sites in the polymer and it is projected that this result will enhance the design and nanostructuring of PPy-based membranes and distribution of dopant in the backbone.

scholarly journals Biocatalyzed Sulfoxidation in Presence of Deep Eutectic Solvents

2020 ◽  
Vol 1 (3) ◽  
pp. 290-297
Author(s):  
Gonzalo de Gonzalo
Keyword(s):  
Deep Eutectic Solvents ◽  
Optically Active ◽  
Cofactor Regeneration ◽  
Natural Deep Eutectic Solvents ◽  
Phosphite Dehydrogenase ◽  
Valuable Compounds ◽  
First Time ◽  
Substrate Concentrations

The flavin-containing monooxygenase from Methylophaga sp. strain SK1 (mFMO) is a valuable biocatalyst for the preparation of optically active sulfoxides, among other valuable compounds. In this study, we explored to benefits of using Natural Deep Eutectic Solvents (NADESs) when doing oxidation with this biocatalyst, fused to phosphite dehydrogenase for cofactor regeneration (PTDH-mFMO). It was found that optically active sulfoxides could be obtained with slightly higher conversions in 10% v/v NADES when working at substrate concentrations of 50–200 mM, whereas there was no loss in the enantioselectivity. With these results, it is demonstrated for the first time that flavin-containing monooxygenases can be employed as biocatalysts in presence of NADESs.

Ultrasonic-Vibration-Assisted Grinding of Brittle Materials: A Mechanistic Model for Cutting Force

2011 ◽  
Author(s):  
Na Qin ◽  
Z. J. Pei ◽  
W. L. Cong ◽  
C. Treadwell ◽  
D. M. Guo
Keyword(s):  
Cutting Force ◽  
Ultrasonic Vibration ◽  
Material Removal ◽  
Mechanistic Model ◽  
Brittle Materials ◽  
Rotary Ultrasonic Machining ◽  
Input Variables ◽  
Diamond Grain ◽  
First Time ◽  
Ultrasonic Vibration Assisted Grinding

A mechanistic model for cutting force in ultrasonic-vibration-assisted grinding (UVAG) (also called rotary ultrasonic machining) of brittle materials is proposed for the first time. Fundamental assumptions include: (1) brittle fracture is the dominant mechanism of material removal, and (2) the removed volume by each diamond grain in one vibration cycle can be related to its indentation volume in the workpiece through a mechanistic parameter. Experiments with UVAG of silicon are conducted to determine the mechanistic parameter for silicon. With the developed model, influences of six input variables on cutting force are predicted. These predicted influences trends are also compared with those determined experimentally for several brittle materials.

Mechanistic Model for High Speed Turning of Austempered Ductile Irons

2012 ◽  
Vol 498 ◽  
pp. 163-168
Author(s):  
A. Fernández ◽  
Gorka Urbikain Pelayo ◽  
A. Rodríguez ◽  
A. Calleja ◽  
L.N. López de Lacalle
Keyword(s):  
Cutting Forces ◽  
High Speed ◽  
Mechanistic Model ◽  
Dry Turning ◽  
High Speed Turning ◽  
First Time

This work proposes a mechanistic model to predict the cutting forces during machining of low machinability materials such as austempered ductile irons (ADI). For these cases, commonly used models are not accurate due to high rates of wear and a new coefficient is necessary to correctly estimate the cutting forces against time. As well, ceramic inserts are applied for the first time in dry turning of ADI.

scholarly journals On the Mechanism of the Thermal Rearrangement of 4-Alkyl-4H-1,2,4-Triazoles. Synthesis and Reaction of Optically Active Triazoles.

1990 ◽  
Vol 44 ◽  
pp. 485-488 ◽  
Author(s):  
Per H. J. Carlsen ◽  
Odd Reidar Gautun ◽  
Dagfinn W. Aksnes ◽  
Trond Brekke ◽  
Knut Maartmann-Moe ◽  
...  
Keyword(s):  
Optically Active ◽  
Thermal Rearrangement
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