Interactions gauches et chemins réactionnels. Etudes conformationnelles d'hydroxyalkyl-4 cyclohexènes contraints

1981 ◽  
Vol 59 (5) ◽  
pp. 859-864
Author(s):  
Jeanine Bouteiller-Prati ◽  
Jean-Claude Bouteiller ◽  
Jean-Pierre Aycard
Keyword(s):  
Free Energy ◽  
Reaction Path ◽  
High Energy ◽  
Nmr Study ◽  
Conformational Equilibria ◽  
The Stability ◽  
Cis And Trans ◽  
Conformational Free Energy

From J and δ values determined by the nmr study of alcohols obtained by addition of CH3Li and LiAlH4 to the exocyclic carbonyl of cis and trans 3-alkyl 4-carbomethoxy (or acetyl) cyclohexenes (alkyl = H, CH3, C(CH3)3), we have deduced the conformational free energy values (ΔG0X) of the CH(CH3)OH and C(CH3)2OH substituents (0.62 and 2.08 kcal mol−1 respectively) as well as the values for some related conformational equilibria. For transtert-butyl derivatives the stability of the diaxial conformer agrees with a reaction path involving high energy conformers.

Nuclear magnetic resonance studies. XV. Conformational free energy of the formyl group

1967 ◽  
Vol 45 (23) ◽  
pp. 2955-2961 ◽  
Author(s):  
G. W. Buchanan ◽  
J. B. Stothers ◽  
Siu-Tzyy Wu
Keyword(s):  
Free Energy ◽  
Solvent Polarity ◽  
Formyl Group ◽  
Proton Spectroscopy ◽  
Kcal Mole ◽  
Magnetic Resonance Studies ◽  
Average Value ◽  
Cis And Trans ◽  
Line Positions ◽  
Conformational Free Energy

Proton spectroscopy has been employed to determine the conformational free energy (− ΔG0) of a formyl group bonded to a cyclohexane ring. The cis- and trans-4-t-butyl derivatives were used as models for the axial and equatorial formyl groups in cyclohexanecarboxaldehyde and 1-methylcyclohexanecarboxaldehyde. The wiggle-beat technique was used to determine the spectral line positions and separations because of the relatively small differences involved. The − ΔG0 values were found to be relatively insensitive to solvent polarity and concentration over the range 10–50 mole %. For 10 mole % solutions the average value of − ΔG0CHO was found to be 1.38 kcal/mole.

scholarly journals Impact of Thermal Fluctuations on Logarithmic Corrected Massive Gravity Charged Black Hole

Entropy ◽  
2021 ◽  
Vol 23 (10) ◽  
pp. 1269
Author(s):  
Abdul Jawad ◽  
Shahid Chaudhary ◽  
Kazuharu Bamba
Keyword(s):  
Black Hole ◽  
Free Energy ◽  
Thermal Fluctuations ◽  
High Energy ◽  
Massive Gravity ◽  
Charged Black Hole ◽  
Nonlinearity Parameter ◽  
Thermodynamic Quantities ◽  
Substantial Impact ◽  
The Stability

We investigate the influence of the first-order correction of entropy caused by thermal quantum fluctuations on the thermodynamics of a logarithmic corrected charged black hole in massive gravity. For this black hole, we explore the thermodynamic quantities, such as entropy, Helmholtz free energy, internal energy, enthalpy, Gibbs free energy and specific heat. We discuss the influence of the topology of the event horizon, dimensions and nonlinearity parameter on the local and global stability of the black hole. As a result, it is found that the holographic dual parameter vanishes. This means that the thermal corrections have no significant role to disturb the holographic duality of the logarithmic charged black hole in massive gravity, although the thermal corrections have a substantial impact on the thermodynamic quantities in the high-energy limit and the stability conditions of black holes.

Novel stereochemical equilibria in crown ethers. Detection of additional conformations of cis-syn-cis- and cis-anti-cis-dicyclohexano-18-crown-6 by 100.6-MHz 13C nuclear magnetic resonance at 173 K

1985 ◽  
Vol 63 (10) ◽  
pp. 2747-2751 ◽  
Author(s):  
G. W. Buchanan ◽  
K. Bourque ◽  
J. W. Bovenkamp ◽  
A. Rodrigue
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Free Energy ◽  
Magnetic Resonance ◽  
Low Temperature ◽  
Crown Ethers ◽  
High Field ◽  
13C Nuclear Magnetic Resonance ◽  
Conformational Equilibria ◽  
Conformational Free Energy ◽  
C Nmr

High field, 13C nmr has been utilized for the analysis of new conformational equilibria in each of the title crown ethers at low temperature. Evidence indicates that these equilibria arise from restricted rotation in the macrocyclic portions of these molecules. The conformational free energy differences between the isomers are small (0.1–0.3 kcal/mol) while barriers to their interconversion are of the order of 8.5–9.0 kcal/mol. Comparisons are made with the degenerate equilibria involving inversion of the cyclohexane rings.

Dicyclohexylethyleneglycol, -diethyleneglycol, -triethyleneglycol, and related monosubstituted cyclohexanes. Conformational analysis using low-temperature 13C and 1H NMR spectroscopy

1995 ◽  
Vol 73 (4) ◽  
pp. 566-572 ◽  
Author(s):  
G.W. Buchanan ◽  
A. Moghimi ◽  
V.M. Reynolds ◽  
K. Bourque
Keyword(s):  
Free Energy ◽  
Nmr Spectroscopy ◽  
1H Nmr Spectroscopy ◽  
Ring Inversion ◽  
Ethylene Glycols ◽  
Axial Conformer ◽  
Conformational Equilibria ◽  
Single Ring ◽  
Conformational Free Energy ◽  
C Nmr

Two conformations of each of the title molecules have been detected by 100 MHz 13C NMR at 210 K. For the dicyclohexyl systems, the conformations are related via a single ring inversion. In each case the equatorial–axial conformer is 4.7 ± 0.4 kJ/mol less stable than the diequatorially substituted form in CD2Cl2 solution. For monosubstituted models, the conformational free energy (−ΔG0) values of the -O-CH2-CH2-OCH3, -OCH2-CH2-O-CH2-CH3, and -O-CH2-CH2-O-CH-(CH3)2 groups have been determined to be 5.4,6.1, and 6.1 ± 0.2 kJ/mol, respectively. In methanol, the latter equilibria are slightly more biased towards the axially substituted conformers. Keywords: substituted ethylene glycols, conformational equilibria.

Stability of radical anions derived from substituted 5-nitrofurans investigated by ESR spectroscopy

1985 ◽  
Vol 50 (7) ◽  
pp. 1594-1601 ◽  
Author(s):  
Jiří Klíma ◽  
Larisa Baumane ◽  
Janis Stradinš ◽  
Jiří Volke ◽  
Romualds Gavars
Keyword(s):  
Radical Anion ◽  
High Stability ◽  
Esr Spectroscopy ◽  
Reaction Path ◽  
Order Reaction ◽  
Second Order ◽  
Radical Anions ◽  
Second Order Reaction ◽  
Unpaired Electron Density ◽  
The Stability

It has been found that the decay in dimethylformamide and dimethylformamide-water mixtures of radical anions in five of the investigated 5-nitrofurans is governed by a second-order reaction. Only the decay of the radical anion generated from 5-nitro-2-furfural III may be described by an equation including parallel first- and second-order reactions; this behaviour is evidently caused by the relatively high stability of the corresponding dianion, this being an intermediate in the reaction path. The presence of a larger conjugated system in the substituent in position 2 results in a decrease of the unpaired electron density in the nitro group and, consequently, an increase in the stability of the corresponding radical anions.

Examining sharp restart in a Monte Carlo method for the linearized Poisson–Boltzmann equation

2020 ◽  
Vol 26 (3) ◽  
pp. 223-244
Author(s):  
W. John Thrasher ◽  
Michael Mascagni
Keyword(s):  
Monte Carlo ◽  
Free Energy ◽  
Monte Carlo Algorithm ◽  
Significant Bias ◽  
Poisson Boltzmann ◽  
Electrostatic Free Energy ◽  
Poisson Boltzmann Equation ◽  
The Stability ◽  
Potential Methods ◽  
The Individual

AbstractIt has been shown that when using a Monte Carlo algorithm to estimate the electrostatic free energy of a biomolecule in a solution, individual random walks can become entrapped in the geometry. We examine a proposed solution, using a sharp restart during the Walk-on-Subdomains step, in more detail. We show that the point at which this solution introduces significant bias is related to properties intrinsic to the molecule being examined. We also examine two potential methods of generating a sharp restart point and show that they both cause no significant bias in the examined molecules and increase the stability of the run times of the individual walks.

Characterization of Textured Aluminum Lines and Modelling of Stress Voiding

1994 ◽  
Vol 343 ◽  
Author(s):  
S.C. Wardle ◽  
B.L. Adams ◽  
C.S. Nichols ◽  
D.A. Smith
Keyword(s):  
Free Energy ◽  
Excess Free Energy ◽  
Mean Field ◽  
High Energy ◽  
Polycrystalline Structure ◽  
Field Approach ◽  
Bamboo Structure ◽  
Automated Technique ◽  
Theory And Modeling

ABSTRACTIt is well known from studies of individual interfaces that grain boundaries exhibit a spectrum of properties because their structure is misorientation dependent. Usually this variability is neglected and properties are modeled using a mean field approach. The limitations inherent in this approach can be overcome, in principle, using a combination of experimental techniques, theory and modeling. The bamboo structure of an interconnect is a particularly simple polycrystalline structure that can now be readily characterized experimentally and modeled in the computer. The grain misorientations in a [111] textured aluminum line have been measured using the new automated technique of orientational imaging microscopy. By relating boundary angle to diffusivity the expected stress voiding failure processes can be predicted through the link between misorientation angle, grain boundary excess free energy and diffusivity. Consequently it can be shown that the high energy boundaries are the favored failure sites thermodynamically and kinetically.

scholarly journals High stability of trehalose/maltose binding protein fromThermococcus litoralismakes it a good candidate as a sensitive element in biosensor systems for sugar control

2010 ◽  
Vol 24 (3-4) ◽  
pp. 349-353 ◽  
Author(s):  
Olga I. Povarova ◽  
Olga V. Stepanenko ◽  
Anna I. Sulatskaya ◽  
Irina M. Kuznetsova ◽  
Konstantin K. Turoverov ◽  
...  
Keyword(s):  
Free Energy ◽  
Sensitive Element ◽  
High Stability ◽  
Binding Protein ◽  
Maltose Binding Protein ◽  
Thermococcus Litoralis ◽  
Thermophilic Archaeon ◽  
Unfolded State ◽  
The Stability ◽  
Innate Ability

Fluorescence and circular dichroism in far-UV region were used to study the stability of trehalose/maltose binding protein (TMBP) from hyper thermophilic archaeonThermococcus litoralisand its complex with glucose (TMBP/Glc). The evaluation of difference between free energy of native and unfolded state for TMBP and TMBP/Glc showed that both of them are several times higher than that of proteins from mesophilic organisms. Due to the high stability and innate ability to bind glucose this protein is a good candidate as a sensitive element in biosensor systems for sugar control.

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