scholarly journals A comparison of pathway-independent and pathway-dependent methods in the calculation of conformational free enthalpy differences

2015 ◽  
Vol 25 (1) ◽  
pp. 184-191 ◽  
Author(s):  
Zhixiong Lin ◽  
Wilfred F. van Gunsteren
Keyword(s):  
Free Enthalpy

A discussion on equations of phase equilibrium between two regular binary phases

1981 ◽  
Vol 46 (6) ◽  
pp. 1433-1438
Author(s):  
Jan Vřešťál
Keyword(s):  
Phase Equilibrium ◽  
Linear Function ◽  
Concentration Dependence ◽  
Absolute Temperature ◽  
Enthalpy Change ◽  
Independent Parameter ◽  
Free Enthalpy ◽  
Regular Solutions ◽  
Regular Model ◽  
Concentration Dependences

The conditions of the existence of extreme on the concentration dependences of absolute temperature (x are mole fractions) T = Tα(xkα) and T = Tβ(xkβ) denoting equilibrium between two binary regular solutions are generally developed under two assumptions: 1) Free enthalpy change of pure components k = i, j at transition from phase α to β is a linear function of temperature. 2) Concentration dependence of excess free enthalpy (identical with enthalpy) of solutions α and β, respectively, is described in regular model by one concentration and temperature independent parameter for each individual phase.

Processes and Responses

2017 ◽  
Author(s):  
Jochen Rau
Keyword(s):  
Heat Engine ◽  
Cyclic Process ◽  
Free Enthalpy ◽  
Initial State ◽  
Thermodynamic Potentials ◽  
Grand Potential ◽  
Laws Of Thermodynamics ◽  
Cyclic Processes ◽  
Energy Exchanges ◽  
Thermodynamic Processes

Thermodynamic processes involve energy exchanges in the forms of work, heat, or particles. Such exchanges might be reversible or irreversible, and they might be controlled by barriers or reservoirs. A cyclic process takes a system through several states and eventually back to its initial state; it may convert heat into work (engine) or vice versa (heat pump). This chapter defines work and heat mathematically and investigates their respective properties, in particular their impact on entropy. It discusses the roles of barriers and reservoirs and introduces cyclic processes. Basic constraints imposed by the laws of thermodynamics are considered, in particular on the efficiency of a heat engine. The chapter also introduces the thermodynamic potentials: free energy, enthalpy, free enthalpy, and grand potential. These are used to describe energy exchanges and equilibrium in the presence of reservoirs. Finally, this chapter considers thermodynamic coefficients which characterize the response of a system to heating, compression, and other external actions.

Rotationsbarriere der Endgruppen bei Poly- methinoxonolen verschiedener Kettenlänge / Rotation Barrier of the End Groups of Polymethine Oxonols with Different Chain Lengths

1976 ◽  
Vol 31 (8) ◽  
pp. 1017-1018 ◽  
Author(s):  
H. Oehling ◽  
F. Baer
Keyword(s):  
Nmr Spectra ◽  
Rotation Barrier ◽  
Free Enthalpy ◽  
Temperature Dependent ◽  
Restricted Rotation ◽  
H Nmr ◽  
Enthalpy Of Activation ◽  
End Groups ◽  
Electron Contribution ◽  
Chain Lengths

Abstract Polymethine oxonols show temperature dependent 1H-NMR-spectra because of restricted rotation of the end groups. The dependence of the value of the corresponding free enthalpy of activation AGt on the length of the poly-methine chain can be explained by the change of the π-electron contribution to ⊿G≠.

Zur Thermodynamik der hydrophoben Wechselwirkung; die Systeme Wasser + Glycin+ Harnstoff und Wasser + Alanin+ Harnstoff bei 25 °C / Thermodynamics of Hydrophobie Interaction in the Systems Water + Glycin + Urea and Water + Alanin + Urea at 25 °C

1973 ◽  
Vol 28 (9-10) ◽  
pp. 533-554 ◽  
Author(s):  
Lothar Rafflenbeul ◽  
Wa-Ming Pang ◽  
Hansjürgen Schönert ◽  
Klaus Haberle
Keyword(s):  
Amino Acid ◽  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Pressure Measurements ◽  
Free Enthalpy ◽  
Heat Of Dilution ◽  
Ternary Solutions ◽  
Vapor Pressure Measurements ◽  
Calorimetric Determination

Abstract Isopiestic vapor pressure measurements and calorimetric determination of the heat of dilution have been performed and evaluated with respect to enthalpy, entropy and free enthalpy in the ternary solutions water+ glycin+ urea and water+ alanin + urea. The free enthalpy of transfer for the process: Amino acid from water to water+ urea, which can be derived from these measurements, does not agree with the value calculated from solubility measurements. The reason for this discrepancy and the values of entropy and enthalpy in terms of hydrophobic interaction are discussed. Supplementary measurements of the proton magnetic resonance in these solutions are included.

Thermodynamics of In Situ Formation of Mg2Si and MgO in AZ91D /Flyash Composites

2011 ◽  
Vol 686 ◽  
pp. 378-381
Author(s):  
Si Rong Yu ◽  
Zhi Qiu Huang ◽  
Jia An Liu
Keyword(s):  
Fly Ash ◽  
Thermodynamic Calculation ◽  
Interfacial Reactions ◽  
Mg Alloy ◽  
Free Enthalpy ◽  
Alloy Matrix ◽  
Microstructure Observation ◽  
Enthalpy Changes ◽  
Fly Ash Cenospheres

Novel AZ91D Mg alloy/fly-ash cenospheres (AZ91D/FAC) composites were fabricated by melt stir technique. The thermodynamic analyses of the interfacial reactions, the microstructure observation, and the phase analyses of the AZ91D/FAC composites were investigated. The results showed that the cenospheres were almost filled with Mg alloy matrix. In-situ MgO and Mg2Si phases were formed in Mg alloy matrix and near the interfaces between the cenospheres and Mg alloy matrix. Through the thermodynamic calculation, it can be found that the standard free enthalpy changes of these interfacial reactions are all negative at the temperature of Mg alloy melt preparation in this work, and these reactions can occur.

Beziehungen zwischen Rotationsisomerie, Wasserstoffbrücken-Bindung und Substituenteneffekten der organischen Chemie / Relations between Rotational Isomerism, Hydrogen Bonding, and Substituent Effects in Organic Chemistry

1972 ◽  
Vol 27 (6) ◽  
pp. 663-674 ◽  
Author(s):  
Gotthard H. Krause ◽  
Herbert Hoyer
Keyword(s):  
Hydrogen Bonding ◽  
Substituent Effects ◽  
Intramolecular Hydrogen Bonding ◽  
Rotational Isomerism ◽  
Proton Acceptor ◽  
Single Bond ◽  
Free Enthalpy ◽  
Acceptor Group ◽  
Intramolecular Hydrogen ◽  
Derivatives Of

The change of free enthalpy involved in intramolecular hydrogen bonding is smaller if the proton acceptor group can rotate round a single bond, as compared to proton acceptor groups which are fixed in a position optimal for hydrogen bonding. Also, the free enthalpy change is altered when the rotation of the proton acceptor is sterically restricted. This is demonstrated by comparing the absorptions of carbonyl stretching vibrations in the infrared spectra of certain compounds showing rotational isomerism. In the present study derivatives of 5-hydroxy-2,2-dimethyl-6-carbomethoxychromanone- (4), 3-nitrosalicylaldehyde and 3-nitro-2-hydroxy-acetophenones substituted in the position 5 and 6 are examined.

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