The dielectric properties of 1,1-dichlorocyclohexane in a supercooled region

1970 ◽  
Vol 48 (19) ◽  
pp. 2983-2987 ◽  
Author(s):  
R. K. Chan ◽  
W. L. Clayton
Keyword(s):  
Free Energy ◽  
Dielectric Relaxation ◽  
Energy Barrier ◽  
Nucleation Theory ◽  
Energy Of Activation ◽  
Free Energy Barrier ◽  
Kcal Mole ◽  
Spontaneous Crystallization ◽  
Crystal Nucleus ◽  
Free Energy Of Activation

From dielectric constant measurements of supercooled 1,1-dichlorocyclohexane in the anomalous dispersion region, the free energy, entropy, and enthalpy of activation for dielectric relaxation are found to be 4.05 kcal mole−1, 123 cal °K−1 mole−1, and 22.3 kcal mole−1, respectively, at −125 °C. The calculated maximum free energy barrier of crystal nucleus formation based on simple nucleation theory is 3.64 kcal mole−1. In view of the qualitative agreement between the experimental free energy of activation of dielectric relaxation and the calculated free energy of activation of nucleation, it is reasonable to conclude that the processes of molecular orientation and of crystal nucleus growth are similar. A calculation of the free energy barrier vs. crystal nucleus size diagram also predicts spontaneous crystallization when the radius of crystal nuclei exceeds 12.8 Å.

Transition path time distribution and the transition path free energy barrier

2016 ◽  
Vol 18 (41) ◽  
pp. 28872-28882 ◽  
Author(s):  
Eli Pollak
Keyword(s):  
Free Energy ◽  
Energy Barrier ◽  
Time Distribution ◽  
Energy Of Activation ◽  
Free Energy Barrier ◽  
Energy Profile ◽  
Transition Path ◽  
Free Energy Profile ◽  
Free Energy Of Activation

Free energy profile, showing why the transition path barrier is lower than the free energy of activation.

Simulating nucleation of molecular solids

2007 ◽  
Vol 463 (2087) ◽  
pp. 2799-2811 ◽  
Author(s):  
Simon Black
Keyword(s):  
Free Energy ◽  
Energy Barrier ◽  
Enthalpy Change ◽  
Enthalpy Of Fusion ◽  
Nucleation Theory ◽  
Molecular Solids ◽  
Free Energy Barrier ◽  
Activation Free Energy ◽  
Entropy Of Fusion ◽  
Metastable Zone

The activation free energy for nucleation of crystals from melts and solutions is described and simulated in a different way from traditional nucleation theory. For molecules at the surface of a nucleus, the unfavourable entropy of fusion outweighs the favourable enthalpy change. The free energy barrier to nucleation in pure melts is simulated from the entropy and enthalpy of fusion. By incorporating the unfavourable entropy of unmixing, nucleation from impure melts and solutions is also simulated. The nature of the metastable zone alters and its size is estimated.

Viscosity of Dimethyl Sulfoxide + 1,4 Dimethylbenzene System

2008 ◽  
Vol 59 (1) ◽  
pp. 45-48
Author(s):  
Oana Ciocirlan ◽  
Olga Iulian
Keyword(s):  
Free Energy ◽  
Dimethyl Sulfoxide ◽  
Atmospheric Pressure ◽  
Entire Range ◽  
Polynomial Equation ◽  
Energy Of Activation ◽  
Excess Gibbs Free Energy ◽  
Experimental Measurements ◽  
Gibbs Energy Of Activation ◽  
Free Energy Of Activation

This paper reports the viscosities measurements for the binary system dimethyl sulfoxide + 1,4-dimethylbenzene over the entire range of mole fraction at 298.15, 303.15, 313.15 and 323.15 K and atmospheric pressure. The experimental viscosities were correlated with the equations of Grunberg-Nissan, Katti-Chaudhri, Hind, Soliman and McAllister; the adjustable binary parameters have been obtained. The excess Gibbs energy of activation of viscous flow (G*E) has been calculated from the experimental measurements and the results were fitted to Redlich-Kister polynomial equation. The obtained negative excess Gibbs free energy of activation and negative Grunberg-Nissan interaction parameter are discussed in structural and interactional terms.

DFT study on the hydrolysis of metsulfuron-methyl: A sulfonylurea herbicide

2018 ◽  
Vol 17 (08) ◽  
pp. 1850050 ◽  
Author(s):  
Qiuhan Luo ◽  
Gang Li ◽  
Junping Xiao ◽  
Chunhui Yin ◽  
Yahui He ◽  
...  
Keyword(s):  
Free Energy ◽  
Water Molecule ◽  
Carbonyl Group ◽  
Energy Barrier ◽  
Density Functional ◽  
Free Energy Barrier ◽  
Functional Theory ◽  
Metsulfuron Methyl ◽  
Catalytic Role ◽  
Hydrolysis Of

Sulfonylureas are an important group of herbicides widely used for a range of weeds and grasses control particularly in cereals. However, some of them tend to persist for years in environments. Hydrolysis is the primary pathway for their degradation. To understand the hydrolysis behavior of sulfonylurea herbicides, the hydrolysis mechanism of metsulfuron-methyl, a typical sulfonylurea, was investigated using density functional theory (DFT) at the B3LYP/6-31[Formula: see text]G(d,p) level. The hydrolysis of metsulfuron-methyl resembles nucleophilic substitution by a water molecule attacking the carbonyl group from aryl side (pathway a) or from heterocycle side (pathway b). In the direct hydrolysis, the carbonyl group is directly attacked by one water molecule to form benzene sulfonamide or heterocyclic amine; the free energy barrier is about 52–58[Formula: see text]kcal[Formula: see text]mol[Formula: see text]. In the autocatalytic hydrolysis, with the second water molecule acting as a catalyst, the free energy barrier, which is about 43–45[Formula: see text]kcal[Formula: see text]mol[Formula: see text], is remarkably reduced by about 11[Formula: see text]kcal[Formula: see text]mol[Formula: see text]. It is obvious that water molecules play a significant catalytic role during the hydrolysis of sulfonylureas.

Strongly hindered rotation in α,α,2,6-terrachlorotoluene. Stereospecific five-bond coupling. Hyperconjugative contributions to long-range sidechain-ring proton coupling constants

1968 ◽  
Vol 46 (12) ◽  
pp. 2187-2188 ◽  
Author(s):  
T. Schaefer ◽  
R. Schwenk ◽  
C. J. Macdonald ◽  
W. F. Reynolds
Keyword(s):  
Free Energy ◽  
Resonance Spectrum ◽  
Coupling Constants ◽  
Proton Resonance ◽  
Kcal Mole ◽  
Hindered Rotation ◽  
Ring Proton ◽  
Meta Position ◽  
Proton Coupling ◽  
Free Energy Of Activation

At −40 °C the C—H bond of the dichloromethyl group of α,α,2,6-tetrachlorotoluene lies in the plane of the ring. The proton resonance spectrum demonstrates a stereospecific five-bond coupling between the C—H proton and the ring proton in the meta position. The coupling to the para proton is essentially zero as expected from a hyperconjugative mechanism. The free energy of activation of rotation of the dichloromethyl group is about 15 kcal/mole at 25 °C.

The crystal structure of ethyl-Z-3-amino-2-benzoyl-2-butenoate and measurement of the barrier to E,Z-isomerization

1980 ◽  
Vol 58 (17) ◽  
pp. 1821-1828 ◽  
Author(s):  
Gary D. Fallon ◽  
Bryan M. Gatehouse ◽  
Allan Pring ◽  
Ian D. Rae ◽  
Josephine A. Weigold
Keyword(s):  
Crystal Structure ◽  
Nuclear Magnetic Resonance ◽  
Hydrogen Bond ◽  
Free Energy ◽  
Magnetic Resonance ◽  
Energy Of Activation ◽  
X Ray ◽  
X Ray Crystallography ◽  
Free Energy Of Activation ◽  
Nuclear Magnetic

Ethyl-3-amino-2-benzoyl-2-butenoate crystallizes from pentane as either the E (mp 82–84 °C) or the Z-isomer (mp 95.5–96.5 °C). The E isomer is less stable, and changes spontaneously into the Z, which bas been identified by X-ray crystallography. The structure is characterised by an N–H/ester CO hydrogen bond and a very long C2—C3 bond (1.39 Å). Nuclear magnetic resonance methods have been used to measure the rate of [Formula: see text] isomerization at several temperatures, leading to the estimate that the free energy of activation at 268 K is 56 ± 8 kJ.

COMPARING FOLDING MECHANISMS OF DIFFERENT PRION PROTEINS BY Gō MODEL

2013 ◽  
Vol 12 (08) ◽  
pp. 1341004
Author(s):  
XUE WU ◽  
TING FU ◽  
ZHI-LONG XIU ◽  
LIU YIN ◽  
JIN-GUANG WANG ◽  
...  
Keyword(s):  
Free Energy ◽  
Prion Protein ◽  
Energy Barrier ◽  
Prion Proteins ◽  
Coarse Grained ◽  
Transmissible Spongiform Encephalopathies ◽  
Free Energy Barrier ◽  
Spongiform Encephalopathies ◽  
Go Model ◽  
Folding Free Energy

Prions are associated with neurodegenerative diseases induced by transmissible spongiform encephalopathies. The infectious scrapie form is referred to as PrP Sc , which has conformational change from normal prion with predominant α-helical conformation to the abnormal PrP Sc that is rich in β-sheet content. Neurodegenerative diseases have been found from both human and bovine sources, but there are no reports about infected by transmissible spongiform encephalopathies from rabbit, canine and horse sources. Here we used coarse-grained Gō model to compare the difference among human, bovine, rabbit, canine, and horse normal (cellular) prion proteins. The denatured state of normal prion has relation with the conversion from normal to abnormal prion protein, so we used all-atom Gō model to investigate the folding pathway and energy landscape for human prion protein. Through using coarse-grained Gō model, the cooperativity of the five prion proteins was characterized in terms of calorimetric criterion, sigmoidal transition, and free-energy profile. The rabbit and horse prion proteins have higher folding free-energy barrier and cooperativity, and canine prion protein has slightly higher folding free-energy barrier comparing with human and bovine prion proteins. The results from all-atom Gō model confirmed the validity of C α-Gō model. The correlations of our results with previous experimental and theoretical researches were discussed.

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