Theoretical calculations: Can Gibbs free energy for intermolecular complexes be predicted efficiently and accurately?

2007 ◽  
Vol 28 (9) ◽  
pp. 1598-1609 ◽  
Author(s):  
Olexandr Isayev ◽  
Leonid Gorb ◽  
Jerzy Leszczynski
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Theoretical Calculations ◽  
Intermolecular Complexes

scholarly journals Detection of Chemical Weapon Agents Using Spectroscopic Probes: A Computational Study

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Letícia S. Braga ◽  
Érika F. Silva ◽  
Daiana T. Mancini ◽  
Eduardo P. da Rocha ◽  
Elaine F. F. da Cunha ◽  
...  
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Organophosphorus Compounds ◽  
Computational Study ◽  
Theoretical Calculations ◽  
Spectroscopic Properties ◽  
Acetylcholinesterase Inhibition ◽  
Chemical Weapon ◽  
Fast Detection ◽  
Absorption Wavelength

Organophosphorus compounds are organic compounds widely employed in agriculture as well as in chemical weapons. The use in agriculture is due to their insecticidal properties. However, in chemical warfare, the use of organophosphorus is associated with acetylcholinesterase inhibition, which promotes the cholinergic syndromes. In this line, the fast detection of this class of compound is crucial for the determination of environmental exposure. This improved detection will naturally allow for more prompt courses of treatment depending on the contaminant findings. In this perspective, the dipyrrinone oxime (1) was employed for the detection of organophosphorus compounds that are employed as nerve agents, such as cyclosarin, sarin, soman, diethyl chlorophosphate, diisopropylfluorophosphate, 2-(dimethylamino)ethyl N,N-dimethylphosphoramidofluoridate, O-ethyl-S-[2-(diethylamino)ethyl]methylphosphonothioate, O-ethyl-S-[2(diisopropylamino)ethyl] methylphosphonothioate, and O,O-diethyl-S-[2-(diethylamino)ethyl] phosphorothioate, through fluorescent emission. The thermodynamics and kinetic parameters as well as spectroscopic properties of the complexes formed for 1 and all organophosphorus compounds previously cited were investigated by means of theoretical calculations. From our findings, only the diethyl chlorophosphate, 2-(dimethylamino)ethyl N,N-dimethylphosphoramidofluoridate, and O,O-diethyl-S-[2-(diethylamino)ethyl] phosphorothioate emitted fluorescence in the hexane, toluene, chloroform, dichloromethane, methanol, acetonitrile, water, and dimethyl sulfoxide solvents. The study of the absorption wavelength with the most polar solvent showed higher values compared to apolar solvents. In the same solvent, for instance, soman in hexane showed the lowest absorption wavelength value, 324.5 nm, and DCP the highest value, 330.8 nm. This behavior was observed in other tested solvents. The thermodynamic parameters indicate negative Gibbs free energy (ΔG) values for the O-ethyl-S-[2(diisopropylamino)ethyl] methylphosphonothioate with 1 reaction. On the other hand, the sarin and cyclosarin revealed the lowest Gibbs free energy (ΔG‡) values, being kinetically favorable and presenting more reactivity.

scholarly journals Theoretical Calculation of Self-Propagating High-Temperature Synthesis (SHS) Preparation of AlB12

2021 ◽  
Author(s):  
Chao Wang ◽  
Xiaoming Cao ◽  
Mengge Dong ◽  
Lu Zhang ◽  
Jianxing Liu ◽  
...  
Keyword(s):  
Free Energy ◽  
High Temperature ◽  
Theoretical Calculation ◽  
Gibbs Free Energy ◽  
Theoretical Calculations ◽  
Adiabatic Temperature ◽  
Raw Material ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Calculation Results

Although experimental results of preparing AlB12 by self-propagating high-temperature synthesis using Mg-B2O3-Al2O3 as raw material has been studied, the theoretical calculations for the preparation of AlB12 have not been examined as thoroughly. In this article, for the first time, we report on the study of theoretical calculation and the adiabatic temperature, calculated, and compared with the actual reaction temperature. The Gibbs free energy for each level of reaction is also calculated. The calculation results show that the adiabatic temperature is 2789.5 K, the standard Gibbs free energy of each reaction is less than 0, and the reaction can proceed spontaneously, which is consistent with the results of the experiment. <br>

scholarly journals Theoretical Calculation of Self-Propagating High-Temperature Synthesis (SHS) Preparation of AlB12

2021 ◽  
Author(s):  
Chao Wang ◽  
Xiaoming Cao ◽  
Mengge Dong ◽  
Lu Zhang ◽  
Jianxing Liu ◽  
...  
Keyword(s):  
Free Energy ◽  
High Temperature ◽  
Theoretical Calculation ◽  
Gibbs Free Energy ◽  
Theoretical Calculations ◽  
Adiabatic Temperature ◽  
Raw Material ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Calculation Results

Although experimental results of preparing AlB12 by self-propagating high-temperature synthesis using Mg-B2O3-Al2O3 as raw material has been studied, the theoretical calculations for the preparation of AlB12 have not been examined as thoroughly. In this article, for the first time, we report on the study of theoretical calculation and the adiabatic temperature, calculated, and compared with the actual reaction temperature. The Gibbs free energy for each level of reaction is also calculated. The calculation results show that the adiabatic temperature is 2789.5 K, the standard Gibbs free energy of each reaction is less than 0, and the reaction can proceed spontaneously, which is consistent with the results of the experiment. <br>

scholarly journals A Theoretical Study of Substituted Cyclobutanones and Their Enols

2004 ◽  
Vol 59 (11) ◽  
pp. 838-844
Author(s):  
Mohammad I. Sway ◽  
Iyad D. Al-Shawabkeh ◽  
Salim M. Khalil
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Theoretical Study ◽  
Theoretical Calculations ◽  
Heats Of Formation ◽  
Geometrical Parameters ◽  
Electron Densities ◽  
Complete Optimization ◽  
Electron Withdrawing Substituents

MINDO-Forces calculations have been performed with complete optimization of the geometry on cyclobutanone and its enol counterpart, perfluorination of cyclobutanones and enol counterparts, and X-cycolobutanones and their X-enols, where X is NO2, CF3, CN, OH, NH2 and F. It was found that ketone is more stable than its enol counterpart. Perfluorination destabilizes ketone on the expense of enol. These results agree with experimental and theoretical calculations. Electron releasing substituents (NH2, OH, F) stabilize cyclobutanone, while electron withdrawing substituents (CF3, NO2) destabilize it. CN substituents have almost no effect on the stabilization of this keto-enol system. Geometrical parameters, heats of formation, electron densities and Gibbs free energy are reported

Chemical equilibrium and chemical kinetics

2018 ◽  
Author(s):  
Dennis Sherwood ◽  
Paul Dalby
Keyword(s):  
Free Energy ◽  
Equilibrium Constant ◽  
Gibbs Free Energy ◽  
Chemical Kinetics ◽  
Chemical Equilibrium ◽  
First Principles ◽  
Effect Of Temperature ◽  
Total System ◽  
Free Energies

Building on the previous chapter, this chapter examines gas phase chemical equilibrium, and the equilibrium constant. This chapter takes a rigorous, yet very clear, ‘first principles’ approach, expressing the total Gibbs free energy of a reaction mixture at any time as the sum of the instantaneous Gibbs free energies of each component, as expressed in terms of the extent-of-reaction. The equilibrium reaction mixture is then defined as the point at which the total system Gibbs free energy is a minimum, from which concepts such as the equilibrium constant emerge. The chapter also explores the temperature dependence of equilibrium, this being one example of Le Chatelier’s principle. Finally, the chapter links thermodynamics to chemical kinetics by showing how the equilibrium constant is the ratio of the forward and backward rate constants. We also introduce the Arrhenius equation, closing with a discussion of the overall effect of temperature on chemical equilibrium.

Extended Gibbs Free Energy and Laplace Pressure of Ordered Hexagonal Close-Packed Spherical Particles: A Wettability Study

Langmuir ◽  
2021 ◽  
Author(s):  
Amir Bayat ◽  
Mahdi Ebrahimi ◽  
Saeed Rahemi Ardekani ◽  
Esmaiel Saievar Iranizad ◽  
Alireza Zaker Moshfegh
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Laplace Pressure ◽  
Spherical Particles ◽  
Hexagonal Close Packed
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