Theoretical Studies on the Effect of the Medium on Tautomeric Phenomena in Neutral and Protonated Acridin-9-amine. Mechanism of Tautomerization in Neutral Entities

1997 ◽  
Vol 50 (2) ◽  
pp. 97 ◽  
Author(s):  
Janusz Rak ◽  
Piotr Skurski ◽  
Ludwika Jozwiak ◽  
Jerzy Blazejowski
Keyword(s):  
High Pressure ◽  
Liquid Phase ◽  
Gaseous Phase ◽  
Dipole Moments ◽  
State Level ◽  
Theoretical Studies ◽  
Pressure Limit ◽  
Energy Gaps ◽  
Tautomeric Forms ◽  
Physicochemical Features

Semiempirical AM1 and PM3 (gaseous phase) and AM1-COSMO, PM3-COSMO and PM3-AQ (liquid phase) methods were used to examine the structure, as well as the thermodynamic and physicochemical features (dipole moments and LUMO and HOMO energies), of tautomeric forms of neutral, mono- and di-protonated acridin-9-amine. The energy gaps between possible tautomers are only insignificantly influenced by the medium and reveal the coexistence of neutral and diprotonated entities in two forms, and the monoprotonated entity in one form. Entropy and thermal energy, which can be evaluated only for gaseous systems on the basis of statistical mechanics, both increase with temperature and affect equilibria between tautomers. The mechanism of bimolecular tautomerization of neutral acridin-9-amine was examinated by the PM3 and PM3-AQ methods. The inclusion of entropy changes accompanying tautomerization in the gaseous phase enabled high-pressure-limit rate constants for well-defined steps of the process at the RRKM and transition state level of theory to be predicted. Thermodynamic and kinetic considerations indicate that neutral acridin-9-amine should coexist in amino and imino tautomeric forms, and that both these entities can convert into each other at moderate temperatures.

ChemInform Abstract: Future of Nano-/Hierarchical Zeolites in Catalysis: Gaseous Phase or Liquid Phase System

ChemInform ◽  
2015 ◽  
Vol 46 (17) ◽  
pp. no-no
Author(s):  
Yueer Yan ◽  
Xiao Guo ◽  
Yahong Zhang ◽  
Yi Tang
Keyword(s):  
Liquid Phase ◽  
Gaseous Phase ◽  
Phase System ◽  
Hierarchical Zeolites

High-pressure liquid-liquid phase change in carbon

1993 ◽  
Vol 48 (6) ◽  
pp. 3591-3599 ◽  
Author(s):  
M. van Thiel ◽  
F. H. Ree
Keyword(s):  
High Pressure ◽  
Liquid Phase ◽  
Phase Change

Are mesoionic compounds aromatic?

1998 ◽  
Vol 76 (6) ◽  
pp. 869-872 ◽  
Author(s):  
Alfredo Mayall Simas ◽  
Joseph Miller ◽  
Petrônio Filgueiras de Athayade Filho
Keyword(s):  
Experimental Evidence ◽  
Key Words ◽  
Dipole Moments ◽  
The Other ◽  
Side Chain ◽  
Theoretical Studies ◽  
X Ray Diffraction ◽  
Ring Plane ◽  
X Ray ◽  
Single Bonds

We have evaluated the experimental evidence relevant to the structure and character of mesoionic compounds, accumulated for more than 100 years and including X-ray diffraction studies. We have also evaluated relevant theoretical studies. All these, including our own extensive work, lead us to conclude that mesoionic compounds are not aromatic. According to our recent definition “mesoionic compounds are planar five-membered heterocyclic betaines with at least one side chain whose α-atom is also in the ring plane and with dipole moments of the order of 5 D. Electrons are delocalized over two regions separated by what are essentially single bonds. One region, which includes the a-atom of the side chain is associated with the HOMO and negative π-charge whereas the other is associated with the LUMO and positive π-charge.” Key words: mesoionic compounds, betaines, aromaticity.

scholarly journals Viscosity Measurement of Olive Oil under Pressure

2021 ◽  
Vol 6 (5) ◽  
Author(s):  
Pawlicki LT
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Phase Transitions ◽  
Liquid Phase ◽  
Olive Oil ◽  
Measurement Method ◽  
Viscosity Measurement ◽  
Food Preservation ◽  
Characteristic Frequencies ◽  
Viscosity Changes

This article presents changes in the viscosity of olive oil during compression. The test was carried out indirectly by measuring the dependence of the resonance frequency of the piezoelectric immersed in olive oil on pressure. For this purpose, for successive pressures, the resonance curves were read and the values of the characteristic frequencies were determined. Viscosity changes were analysed and related to the compression and crystallization taking place in the tested substance. During this research, a phase transition from the liquid phase to the alpha crystalline phase was detected, during which the resonant frequency of the tested piezoelectric reached a minimum and the viscosity related to this frequency reached a maximum. The measurement method developed in this paper can be used to detect the phase transitions of oils subjected to pressure. This may find application in the oil production and high-pressure food preservation industries for which this knowledge is essential for the safe and trouble-free use of their machines.

scholarly journals Fuel spray vapour distribution correlations for a high pressure diesel fuel spray cases for different injector nozzle geometries.

2017 ◽  
Author(s):  
Darlington Njere ◽  
Nwabueze Emekwuru
Keyword(s):  
High Pressure ◽  
Liquid Phase ◽  
Diesel Fuel ◽  
Ambient Pressure ◽  
Vapour Phase ◽  
Fuel Spray ◽  
Combustion Chambers ◽  
Complete Combustion ◽  
Fuel Injectors ◽  
Fuel Vapour

The evolution of diesel fuel injection technology, to facilitate strong correlations of in-cylinder spray propagation with injection conditions and injector geometry, is crucial in facing emission challenges. More observations of spray propagation are, therefore, required to provide valuable information on how to ensure that all the injected fuel has maximum contact with the available air, to promote complete combustion and reduce emissions. In this study, high pressure diesel fuel sprays are injected into a constant-volume chamber at injection and ambient pressure values typical of current diesel engines. For these types of sprays the maximum fuel liquid phase penetration is different and reached sooner than the maximum fuel vapour phase penetration. Thus, the vapour fuel could reach the combustion chamber wall and could be convected and deflected by swirling air. In hot combustion chambers this impingement can be acceptable but this might be less so in larger combustion chambers with cold walls. The fuel-ambient mixture in vapourized fuel spray jets is essential to the efficient performance of these engines. For this work, the fuel vapour penetration values are presented for fuel injectors of different k-factors. The results indicate that the geometry of fuel injectors based on the k-factors appear to affect the vapour phase penetration more than the liquid phase penetration. This is a consequence of the effects of the injector types on the exit velocity of the fuel droplets.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4951

scholarly journals Numerical Analysis of High-Pressure Direct Injection Dual-Fuel Diesel-Liquefied Natural Gas (LNG) Engines

Processes ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 261 ◽  
Author(s):  
Alberto Boretti
Keyword(s):  
High Pressure ◽  
Steady State ◽  
Liquid Phase ◽  
Natural Gas ◽  
Power Density ◽  
Conversion Efficiency ◽  
Liquefied Natural Gas ◽  
Dual Fuel ◽  
Fuel Conversion ◽  
Better Than

Dual fuel engines using diesel and fuels that are gaseous at normal conditions are receiving increasing attention. They permit to achieve the same (or better) than diesel power density and efficiency, steady-state, and substantially similar transient performances. They also permit to deliver better than diesel engine-out emissions for CO2, as well as particulate matter, unburned hydrocarbons, and nitrous oxides. The adoption of injection in the liquid phase permits to further improve the power density as well as the fuel conversion efficiency. Here, a model is developed to study a high-pressure, 1600 bar, liquid phase injector for liquefied natural gas (LNG) in a high compression ratio, high boost engine. The engine features two direct injectors per cylinder, one for the diesel and one for the LNG. The engine also uses mechanically assisted turbocharging (super-turbocharging) to improve the steady-state and transient performances of the engine, decoupling the power supply at the turbine from the power demand at the compressor. Results of steady-state simulations show the ability of the engine to deliver top fuel conversion efficiency, above 48%, and high efficiencies, above 40% over the most part of the engine load and speed range. The novelty of this work is the opportunity to use very high pressure (1600 bar) LNG injection in a dual fuel diesel-LNG engine. It is shown that this high pressure permits to increase the flow rate per unit area; thus, permitting smaller and lighter injectors, of faster actuation, for enhanced injector-shaping capabilities. Without fully exploring the many opportunities to shape the heat release rate curve, simulations suggest two-point improvements in fuel conversion efficiency by increasing the injection pressure.

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