Conformational Analysis of trans-syn-trans-4,5:9,10-Biscyclohexano-1,3,6,8-tetraoxecane: a Low-energy Pathway for Boat–Chair–Boat (BCB) Interconversion

1974 ◽  
Vol 52 (14) ◽  
pp. 2566-2572 ◽  
Author(s):  
T. Bruce Grindley ◽  
Walter A. Szarek
Keyword(s):  
Conformational Analysis ◽  
Variable Temperature ◽  
Membered Ring ◽  
Low Energy ◽  
The Other ◽  
Energy Of Activation ◽  
Conformational Interconversion

Two processes were observed by study of the variable temperature p.m.r. spectra of trans-syn-trans-4,5:9,10-biscyclohexano-1,3,6,8-tetraoxecane (1), one of which, an equilibrium, was still rapid at −88°; the other had an energy of activation (ΔG≠) of 11.7 kcal/mol. These processes are interpreted in terms of interchange in the 10-membered ring between four conformations, namely, two degenerate pairs of diastereomeric boat–chair–boat (BCB) conformations. Possible pathways of conformational interconversion are discussed.

scholarly journals Organocatalysis: A Tool of Choice for the Enantioselective Nucleophilic Dearomatization of Electron-Deficient Six-Membered Ring Azaarenium Salts

Catalysts ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1249
Author(s):  
Claire Segovia ◽  
Pierre-Antoine Nocquet ◽  
Vincent Levacher ◽  
Jean-François Brière ◽  
Sylvain Oudeyer
Keyword(s):  
Asymmetric Catalysis ◽  
Complex Compounds ◽  
Membered Ring ◽  
Low Energy ◽  
The Other ◽  
Great Success ◽  
Chemical Transformations ◽  
3D Scaffolds ◽  
High Level ◽  
Powerful Strategy

Nucleophilic dearomatization of azaarenium salts is a powerful strategy to access 3D scaffolds of interest from easily accessible planar aromatic azaarene compounds. Moreover, this approach yields complex dihydroazaarenes by allowing the functionalization of the scaffold simultaneously to the dearomatization step. On the other side, organocatalysis is nowadays recognized as one of the pillars of the asymmetric catalysis field of research and is well-known to afford a high level of enantioselectivity for a myriad of transformations thanks to well-organized transition states resulting from low-energy interactions (electrostatic and/or H-bonding interactions…). Consequently, in the last fifteen years, organocatalysis has met great success in nucleophilic dearomatization of azaarenium salts. This review summarizes the work achieved up to date in the field of organocatalyzed nucleophilic dearomatization of azaarenium salts (mainly pyridinium, quinolinium, quinolinium and acridinium salts). A classification by organocatalytic mode of activation will be disclosed by shedding light on their related advantages and drawbacks. The versatility of the dearomatization approach will also be demonstrated by discussing several chemical transformations of the resulting dihydroazaarenes towards the synthesis of structurally complex compounds.

Nuclear Magnetic Resonance Evidence for High Barrier of Conformational Inversion in Hexahydro-3,3,7,7-tetramethyl-1,2-oxazepine-5-one

1975 ◽  
Vol 53 (3) ◽  
pp. 414-418 ◽  
Author(s):  
Roderick E. Wasylishen ◽  
Kenner C. Rice ◽  
Ulrich Weiss
Keyword(s):  
Activation Energy ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nitrogen Atom ◽  
Variable Temperature ◽  
Membered Ring ◽  
Rate Process ◽  
Conformational Interconversion ◽  
Nuclear Magnetic

Variable temperature proton n.m.r. spectra indicate an activation energy of 19.0 ± 0.5 kcal/mol for conformational equilibration in hexahydro-3,3,7,7-tetramethyl-1,2-oxazepine-5-one. It is suggested that the rate process involves slow conformational interconversion of the seven-membered ring and not slow inversion at the nitrogen atom. The synthesis of several related 1,2-oxazepines is described.

Isomerization of the Isoprene Hydroxy Nitrates and Formation of Orthonitrite Compounds

2019 ◽  
Author(s):  
Gabriel da Silva
Keyword(s):  
Hydroxy Group ◽  
Peroxyl Radical ◽  
Branching Fractions ◽  
Membered Ring ◽  
Low Energy ◽  
Peroxyl Radicals ◽  
Aerosol Formation ◽  
Subsequent Removal ◽  
Ring Compounds ◽  
Group Migration

Atmospheric oxidation of isoprene produces significant yields of eight unique nitrate 11 compounds, each with a β- or δ-hydroxy group. These isoprene hydroxy nitrates (ISOPNs) 12 significantly impact upon global NOx budgets, O3 levels, and aerosol formation. 13 Uncertainties exist, however, in our understanding of ISOPN chemistry, particularly in their 14 yields from the reaction of isoprene peroxyl radicals with NO. This study describes novel 15 isomerization reactions of the ISOPNs, identified through the application of computational 16 chemistry techniques. These reactions produce saturated polycyclic orthonitrite compounds 17 via attack of the R–NO2 group on the vinyl moiety. For the δ-hydroxy nitrates, low-energy 18 isomerization pathways exist to six-membered ring compounds that are around 5 kcal mol-1 19 exothermic. These reactions proceed with barriers around 15 kcal mol-1 below the 20 respective peroxyl radical + NO reactants and yield orthonitrites that can further isomerize 21 to β-hydroxy ISOPNs. Moreover, the δ-hydroxy nitrates can directly interconvert with their β 22 substituted counterparts via NO3 group migration, with barriers that are lower yet. It follows 23 that β-hydroxy nitrates may be stabilized in the δ-hydroxy form, and vice versa. Moreover, 24 the lowest-energy pathway for dissociation of the δ-hydroxy ISOPNs is for the formation of 25 β-hydroxy alkoxyl radicals, and because of this established branching fractions between the 26 various isoprene peroxyl radicals may require re-evaluation. The results presented here also 27 suggest that ISOPNs may be stabilized to some extent in their saturated orthonitrite forms, 28 which has implications for both the total nitrate yield and for their subsequent removal by 29 OH, O3, and photolysis.<br><br>

scholarly journals Study on the Variable-Temperature Drying Process of Corn Drying in an Industrial Corn-Drying System Equipped with a Self-Adaptive Control Heat Exchanger

2021 ◽  
Vol 11 (6) ◽  
pp. 2772
Author(s):  
Bin Li ◽  
Zhiheng Zeng ◽  
Xuefeng Zhang ◽  
Ye Zhang
Keyword(s):  
Adaptive Control ◽  
Energy Consumption ◽  
Heat Loss ◽  
Thermal Performance ◽  
Variable Temperature ◽  
The Other ◽  
Drying Process ◽  
Drying Kinetic ◽  
Drying System ◽  
Self Adaptive

To realize energy-saving and efficient industrial grain drying, the present work studied the variable-temperature drying process of corn drying in a novel industrial corn-drying system with a heat recycling and self-adaptive control function. The drying kinetics, thermal performance, heat-loss characteristics and the heat-recycling performance of the drying system under different allocations between flue gas and hot air were investigated, and the optimized drying process was proposed and compared with two constant drying processes. The results showed that the optimized drying process exhibited better drying kinetic and thermal performance than the two constant drying processes. More specifically, the total heat loss, total energy consumption and specific energy consumption of the optimized drying process were ascertained to be 36,132.85 MJ, 48,803.99 MJ and 7290.27 kJ/kg, respectively, which were lower than those of the other two processes. On the other hand, the thermal efficiency of the drying chamber for the optimized drying process was ascertained to be varied within the range of 6.81–41.71%. Overall, the validation results showed that the optimized drying process can significantly improve the drying performance of the drying system.

scholarly journals Di-μ-chlorido-bis{[2-(di-tert-butylphosphanyl)biphenyl-3-yl-κ2C3,P]palladium(II)} dichloromethane disolvate

2013 ◽  
Vol 69 (2) ◽  
pp. m86-m86 ◽  
Author(s):  
Cedric W. Holzapfel ◽  
Bernard Omondi
Keyword(s):  
Palladium Complex ◽  
Solvent Molecule ◽  
Membered Ring ◽  
The Other ◽  
Coordination Geometry ◽  
Inversion Center ◽  
Asymmetric Unit ◽  
Coordination Sites ◽  
Square Planar ◽  
Cl Atoms

The asymmetric unit of the title compound, [Pd2Cl2(C20H26P)2]·2CH2Cl2, contains one half-molecule of the palladium complex and a dichloromethane solvent molecule. In the complex, two PdIIatoms are bridged by two Cl atoms, with the other two coordination sites occupied by a C atom of the biphenyl system and a P atom, resulting in a distorted square-planar coordination geometry of the PdIIatom and a cyclometallated four-membered ring. The Pd2Cl2unit is located about an inversion center. The planes of the rings of the biphenyl system make a dihedral angle of 66.36 (11)°.

Instability Study of Repetitive Nanosecond Pulsed Discharge Plasma in a Plasma Assisted Burner

2020 ◽  
Author(s):  
Saeid Zare ◽  
Omid Askari
Keyword(s):  
High Velocity ◽  
Discharge Plasma ◽  
Diffusion Flames ◽  
High Energy ◽  
Discharge Voltage ◽  
Low Energy ◽  
Peak Discharge ◽  
The Other ◽  
Other Hand ◽  
Point To Point

Abstract High velocity flows, as in aerospace applications require special techniques to stabilize and ignite diffusion flames. Some techniques focus on changing parameters like geometry, conditions of the flow, or fuel composition, but these techniques are usually too expensive or impossible due to major changes in the system. On the other hand, some techniques focus on generating a region of charged/excited species and active radicals upstream of the flame. That can substantially enhance the flame stability even under high strain rate or at lean-limit-flammability conditions. Repetitive nanosecond pulsed (RNP) discharge plasma is a nonthermal plasma technique with some remarkable potential to improve stability and ignitability of high velocity diffusion flames. This technique was used in previous papers in a plasma assisted coaxial inverse diffusion burner and showed some promising results by reducing the lift-off height and delaying detachment and blowout conditions. This burner is prepared to employ the discharges at the burner nozzle and simulate a single element of a multi-element methane burner. However, effectiveness of high-voltage high-frequency RNP plasma was limited by the mode of the discharge. During the tests, three different modes were observed at different combinations of plasma and flow conditions. These three modes are low energy corona, uniformly distributed plasma, and high-energy point-to-point discharge. Among these three, only well-distributed plasma significantly improved the flame. In other cases, plasma deployment was either ineffective or in some cases adversely affected the flame by producing undesirable turbulence advancing blow out. As a result, a comprehensive study of these modes is required. In this work, the transition between these three modes in a jet flame was discussed. It has been expressed as a function of plasma conditions, i.e. peak discharge voltage and discharge frequency. It was shown that increasing flow speed delays increases the voltage and frequency at which transition occurs from low-energy corona discharge to well distributed plasma discharge. Subsequently, the effective plasma conditions are thinned. On the other hand, by increasing the frequency of nanosecond discharges, the chance of unstable point-to-point discharges is decreased. In contrast, the discharge peak voltage causes two different consequences. If it is too low, the pulse intensity is too week that the system will experience no visible plasma discharges or the discharges will not pass the low-energy corona, no matter how high the frequency is. If too high, it will enhance the chance of point-to-point discharges and limits the stabilization outcome of the system. Therefore, an optimal region is found for peak discharge voltage.

Smart PCBs for Smart Appliances - Embedding as IoT Enabler

2015 ◽  
Vol 2015 (1) ◽  
pp. 000025-000030
Author(s):  
Nick Renaud-Bezot ◽  
Christian Galler ◽  
Christian Vockenberger
Keyword(s):  
Functional Integration ◽  
Low Energy ◽  
The Other ◽  
Passive Components ◽  
Short Cycle ◽  
Cycle Times ◽  
Smart Appliances ◽  
Fine Pitch ◽  
Low Energy Consumption ◽  
The Eu

Be it the trillion-dollar economy dreamed up by Cisco Systems at one extreme, or the multitude of small crowdsourced projects at the other, there is no denying that IoT is capturing minds and making the news. Each company is vying for a piece of the pie, with semiconductor suppliers scrambling to call the latest releases “IoT-ready”. Not wanting to feel left out, the PCB industry is of course finding ways to support this nascent economy. As main concerns are small sizes, low energy consumption and short cycle times, one solution is embedding. By placing active and passive components within the PCB itself, the system can:- be more integrated, as components disappear from the surface, making space for additional functionality, larger battery or simply fit in a smaller housing,- have lower losses, as stacking SMT components on top of the embedded allows for short connections, thus lowering resistance and inductance,- be created faster, to enable dimensional and functional integration without relying on complex and costly SoC design. Starting with a backgrounder on common embedding technologies currently available from leading suppliers, the paper will present recent advances from AT&S's ECP® (Embedded-Component Packaging), including reliability data. Expanding from that field, the document will explore its future and extreme applications, such as high-power (multi-kW) and fine-pitch fields for industrial and automotive devices, showing the scalability of the technology and the evolutions supported by the EU-funded EmPower and UNSETH projects.

Current-Mode Deep Level Spectroscopy of Vanadium-Doped HPSI 4H-SiC

2020 ◽  
Vol 1004 ◽  
pp. 331-336
Author(s):  
Giovanni Alfieri ◽  
Lukas Kranz ◽  
Andrei Mihaila
Keyword(s):  
Deep Level Transient Spectroscopy ◽  
Scientific Community ◽  
Minority Carrier ◽  
Deep Level ◽  
Current Mode ◽  
Low Energy ◽  
The Other ◽  
Carrier Trap ◽  
Low Energy Electron ◽  
Transient Spectroscopy

SiC has currently attracted the interest of the scientific community for qubit applications. Despite the importance given to the properties of color centers in high-purity semi-insulating SiC, little is known on the electronic properties of defects in this material. In our study, we investigated the presence of electrically active levels in vanadium-doped substrates. Current mode deep level transient spectroscopy, carried out in the dark and under illumination, together with 1-D simulations showed the presence of two electrically active levels, one associated to a majority carrier trap and the other one to a minority carrier trap. The nature of the detected defects has been discussed in the light of the characterization performed on low-energy electron irradiated substrates and previous results found in the literature.

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