Strukturuntersuchungen an chiralen Schiff-Basen des 11-cis-Retinals/Structure Investigation of Chiral Schiff Bases of 11-cis-Retinal

1989 ◽  
Vol 44 (3) ◽  
pp. 333-344 ◽  
Author(s):  
Volker Buß ◽  
Verena Haas ◽  
Ute Wingen
Keyword(s):  
Experimental Data ◽  
Force Field ◽  
Schiff Bases ◽  
Structural Information ◽  
Quantitative Agreement ◽  
Uv Spectra ◽  
Structure Investigation ◽  
Temperature Dependent ◽  
Optimized Geometries ◽  
Hydrogen Bonded

CD and UV spectra of four chiral 11-cis-retinal Schiff bases obtained by condensing the aldehyde with asymmetric amines are used to gain structural information about the polyene conformation. The spectra are temperature-dependent indicating the same 12-s-cis/trans equilibrium as in 11-cis-retinal. In addition, CD absorptions arise at lower temperatures whose only origin is the inherent dissymmetric nature of the retinylidene Chromophore. CNDO /S-calculations performed on the basis of force-field optimized geometries give results which can partially be rationalized on the basis of experimental data. Quantitative agreement is obtained in the case of chiral hydrogen-bonded dimers.

Benchmark of ReaxFF Force Field for Subcritical and Supercritical Water

2018 ◽  
Author(s):  
Hegoi Manzano ◽  
Weiwei Zhang ◽  
Adri C. T. van Duin ◽  
Muralikrishna Raju ◽  
Jorge S. Dolado ◽  
...  
Keyword(s):  
Experimental Data ◽  
Dielectric Constant ◽  
Force Field ◽  
Reaction Mechanisms ◽  
Quantitative Agreement ◽  
Water Molecules ◽  
Constant Diffusion ◽  
Valuable Complement ◽  
Reaxff Force Field ◽  
Waste Separation

<div><div><div><p>Water in the subcritical and supercritical states has remarkable properties that make it an excellent solvent for oxidation of hazardous chemicals, waste separation, and green synthesis. Molecular simulations are a valuable complement to experiments in order to understand and improve the relevant sub- and super-critical reaction mechanisms. Since water molecules under those conditions can act not only as solvent but also as reactant, dissociative force fields are specially interesting to investigate theseprocesses. In this work, we evaluate the capacity of the ReaxFF force field to reproduce the microstructure, hydrogen bonding, dielectric constant, diffusion, and proton transfer of sub- and super-critical water. Our results indicate that ReaxFF is able to simulate water properties in these states in very good quantitative agreement with existing experimental data, with the exception of the static dielectric constant which is reproduced only qualitatively.</p></div></div></div>

Benchmark of ReaxFF Force Field for Subcritical and Supercritical Water

2018 ◽  
Author(s):  
Hegoi Manzano ◽  
Weiwei Zhang ◽  
Adri C. T. van Duin ◽  
Muralikrishna Raju ◽  
Jorge S. Dolado ◽  
...  
Keyword(s):  
Experimental Data ◽  
Dielectric Constant ◽  
Force Field ◽  
Reaction Mechanisms ◽  
Quantitative Agreement ◽  
Water Molecules ◽  
Constant Diffusion ◽  
Valuable Complement ◽  
Reaxff Force Field ◽  
Waste Separation

<div><div><div><p>Water in the subcritical and supercritical states has remarkable properties that make it an excellent solvent for oxidation of hazardous chemicals, waste separation, and green synthesis. Molecular simulations are a valuable complement to experiments in order to understand and improve the relevant sub- and super-critical reaction mechanisms. Since water molecules under those conditions can act not only as solvent but also as reactant, dissociative force fields are specially interesting to investigate theseprocesses. In this work, we evaluate the capacity of the ReaxFF force field to reproduce the microstructure, hydrogen bonding, dielectric constant, diffusion, and proton transfer of sub- and super-critical water. Our results indicate that ReaxFF is able to simulate water properties in these states in very good quantitative agreement with existing experimental data, with the exception of the static dielectric constant which is reproduced only qualitatively.</p></div></div></div>

scholarly journals Comparison between Investigational IR and Crystallographic Data with Computational Chemistry Tools as Validation of the Methods

2010 ◽  
Vol 2010 ◽  
pp. 1-5 ◽  
Author(s):  
U. C. Abdul Jaleel ◽  
M. Rakhila ◽  
Geetha Parameswaran
Keyword(s):  
Experimental Data ◽  
Ir Spectra ◽  
Force Field ◽  
Computational Chemistry ◽  
Schiff Bases ◽  
Density Functional ◽  
Mechanical Force ◽  
Computational Tools ◽  
Density Functional Methods ◽  
Functional Methods

Computational tools, specifically molecular mechanical force field (MM+) and semiempirical (PM3) and density functional methods (DFT) are applied to sets of schiff bases and their complexes. The results are compared with experimental data. It is also found that the simulated IR spectra are in consistence with the experimental data.

Force field for in-plane vibrations of terephthalonitrile

1989 ◽  
Vol 54 (1) ◽  
pp. 18-27 ◽  
Author(s):  
Juan F. Arenas ◽  
Juan I. Marcos ◽  
Francisco J. Ramírez
Keyword(s):  
Experimental Data ◽  
Force Field ◽  
Normal Coordinates ◽  
Internal Coordinates ◽  
Isotopic Shifts ◽  
Quadratic Force Field ◽  
Semi Empirical

The general quadratic force field for the in-plane vibrations of terephthalonitrile was calculated by the semi-empirical MINDO/3 method. This force field was refined to the frequencies observed experimentally for terephthalonitrile and isotopic shifts of terephthalonitrile-[15N2]. The refined frequencies reproduce the experimental data with errors less than 0.5%. The normal coordinates and the force field in internal coordinates were also calculated from the refined field.

A New Dynamic Wettability-Alteration Model for Oil-Wet Cores During Surfactant-Solution Imbibition

SPE Journal ◽  
2013 ◽  
Vol 18 (05) ◽  
pp. 818-828 ◽  
Author(s):  
M. Hosein Kalaei ◽  
Don W. Green ◽  
G. Paul Willhite
Keyword(s):  
Experimental Data ◽  
Oil Recovery ◽  
History Matching ◽  
Mechanistic Model ◽  
Surfactant Solution ◽  
Experimental Tests ◽  
Quantitative Agreement ◽  
Wettability Alteration ◽  
Porous Rock ◽  
Surfactant Solutions

Summary Wettability modification of solid rocks with surfactants is an important process and has the potential to recover oil from reservoirs. When wettability is altered by use of surfactant solutions, capillary pressure, relative permeabilities, and residual oil saturations change wherever the porous rock is contacted by the surfactant. In this study, a mechanistic model is described in which wettability alteration is simulated by a new empirical correlation of the contact angle with surfactant concentration developed from experimental data. This model was tested against results from experimental tests in which oil was displaced from oil-wet cores by imbibition of surfactant solutions. Quantitative agreement between the simulation results of oil displacement and experimental data from the literature was obtained. Simulation of the imbibition of surfactant solution in laboratory-scale cores with the new model demonstrated that wettability alteration is a dynamic process, which plays a significant role in history matching and prediction of oil recovery from oil-wet porous media. In these simulations, the gravity force was the primary cause of the surfactant-solution invasion of the core that changed the rock wettability toward a less oil-wet state.

TEMPERATURE-DEPENDENCE OF PROTON CONDUCTIVITY IN HYDROGEN-BONDED MOLECULAR SYSTEMS

2007 ◽  
Vol 21 (19) ◽  
pp. 1239-1252 ◽  
Author(s):  
XIAO-FENG PANG ◽  
BO DENG ◽  
HUAI-WU ZHANG ◽  
YUAN-PING FENG
Keyword(s):  
Experimental Data ◽  
Electric Field ◽  
Temperature Dependence ◽  
Electric Conductivity ◽  
Proton Conductivity ◽  
Model System ◽  
Time Dependent ◽  
Molecular Systems ◽  
Damping Effect ◽  
Hydrogen Bonded

The temperature-dependence of proton electric conductivity in hydrogen-bonded molecular systems with damping effect was studied. The time-dependent velocity of proton and its mobility are determined from the Hamiltonian of a model system. The calculated mobility of (3.57–3.76) × 10-6 m 2/ Vs for uniform ice is in agreement with the experimental value of (1 - 10) × 10-2 m 2/ Vs . When the temperature and damping effects of the medium are considered, the mobility is found to depend on the temperature for various electric field values in the system, i.e. the mobility increases initially and reaches a maximum at about 191 K, but decreases subsequently to a minimum at approximately 241 K, and increases again in the range of 150–270 K. This behavior agrees with experimental data of ice.

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