scholarly journals Calculation of Five Thermodynamic Molecular Descriptors by Means of a General Computer Algorithm Based on the Group-Additivity Method: Standard Enthalpies of Vaporization, Sublimation and Solvation, and Entropy of Fusion of Ordinary Organic Molecules and Total Phase-Change Entropy of Liquid Crystals

Molecules ◽  
2017 ◽  
Vol 22 (7) ◽  
pp. 1059 ◽  
Author(s):  
Rudolf Naef ◽  
William Acree
Keyword(s):  
Liquid Crystals ◽  
Phase Change ◽  
Organic Molecules ◽  
Molecular Descriptors ◽  
Computer Algorithm ◽  
Group Additivity ◽  
Entropy Of Fusion ◽  
Total Phase ◽  
General Computer

scholarly journals Calculation of Five Thermodynamic Molecular Descriptors by Means of a General Computer Algorithm Based on the Group-Additivity Method: Standard Enthalpies of Vaporization, Sublimation and Solvation, and Entropy of Fusion of ordinary Organic Molecules and Total Phase-Change Entropy of Liquid Crystals

2017 ◽  
Author(s):  
Rudolf Naef ◽  
William E. Acree Jr.
Keyword(s):  
Liquid Crystals ◽  
Phase Change ◽  
Goodness Of Fit ◽  
Cross Validation ◽  
Organic Molecules ◽  
Enthalpy Of Fusion ◽  
Computer Algorithm ◽  
Group Additivity ◽  
Entropy Of Fusion ◽  
Total Phase

The calculation of the standard enthalpies of vaporization, sublimation and solvation of organic molecules is presented using a common computer algorithm on the basis of a group-additivity method. The same algorithm is also shown to enable the calculation of their entropy of fusion as well as the total phase-change entropy of liquid crystals. The present method is based on the complete break-down of the molecules into their constituting atoms and their immediate neighbourhood; the respective calculations of the contribution of the atomic groups by means of the Gauss-Seidel fitting method is based on experimental data collected from literature. The feasibility of the calculations for each of the mentioned descriptors was verified by means of a 10-fold cross-validation procedure proving the good to high quality of the predicted values for the three mentioned enthalpies and for the entropy of fusion, whereas the predictive quality for the total phase-change entropy of liquid crystals was poor. The goodness of fit (Q2) and the standard deviation (σ) of the cross-validation calculations for the five descriptors was as follows: 0.9641 and 4.56 kJ/mol (N=3386 test molecules) for the enthalpy of vaporization, 0.8657 and 11.39 kJ/mol (N=1791) for the enthalpy of sublimation, 0.9546 and 4.34 kJ/mol (N=373) for the enthalpy of solvation, 0.8727 and 17.93 J/mol/K (N=2637) for the entropy of fusion and 0.5804 and 32.79 J/mol/K (N=2643) for the total phase-change entropy of liquid crystals. The large discrepancy between the results of the two closely related entropies is discussed in detail. Molecules, for which both the standard enthalpies of vaporization and sublimation were calculable, enabled the estimation of their standard enthalpy of fusion by simple subtraction of the former from the latter enthalpy. For 990 of them the experimental enthalpy-of-fusion values are also known, allowing their comparison with predictions, yielding a correlation coefficient R2 of 0.6066.

Rationalization of liquid assisted grinding intercalation yields of organic molecules into layered double hydroxides by multivariate analysis

RSC Advances ◽  
2016 ◽  
Vol 6 (110) ◽  
pp. 108431-108439 ◽  
Author(s):  
E. Conterosito ◽  
M. Milanesio ◽  
L. Palin ◽  
V. Gianotti
Keyword(s):  
Multivariate Analysis ◽  
Layered Double Hydroxides ◽  
Organic Molecules ◽  
Molecular Descriptors ◽  
Layered Materials ◽  
Double Hydroxides

PCA, coupled to molecular descriptors, proved to be an effective tool to rationalize the mechanochemical intercalation yields of layered materials.

Electric-Field-Induced Phase Change in Cholesteric Liquid Crystals

1968 ◽  
Vol 20 (19) ◽  
pp. 1024-1025 ◽  
Author(s):  
J. J. Wysocki ◽  
J. Adams ◽  
W. Haas
Keyword(s):  
Liquid Crystals ◽  
Electric Field ◽  
Phase Change ◽  
Cholesteric Liquid Crystals

High-resolution solid-state NMR investigation of the nature of the interaction between organic substrates and the zeolite ZSM-5 lattice

1988 ◽  
Vol 66 (8) ◽  
pp. 1942-1947 ◽  
Author(s):  
C. A. Fyfe ◽  
H. Strobl ◽  
H. Gies ◽  
G. T. Kokotailo
Keyword(s):  
Solid State ◽  
High Resolution ◽  
Phase Change ◽  
Solid State Nmr ◽  
Organic Molecules ◽  
Lattice Structure ◽  
Model System ◽  
Mas Nmr ◽  
Organic Substrates ◽  
Nmr Spectrum

The compounds p-xylene, p-chlorotoluene, and p-dichlorobenzene induce essentially identical changes in the 29Si MAS NMR spectrum of zeolite ZSM-5, indicating that the major contribution to the induced phase change of the lattice structure in these cases is the size and shape of the sorbed organic molecules. Based on these results, p-dichlorobenzene may be used as a model system in future diffraction studies of the sorbate/lattice structure greatly facilitating these investigations.

On the Problem of Heat Transfer in a Phase-Change Slab Initially Not at the Critical Temperature

1987 ◽  
Vol 109 (1) ◽  
pp. 5-9 ◽  
Author(s):  
L. N. Gutman
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Transfer Problem ◽  
Maximum Error ◽  
Additional Time ◽  
Total Phase ◽  
Slab Temperature ◽  
Indirect Evaluation ◽  
Time Required ◽  
Perturbation Problems

A one-dimensional heat transfer problem in the phase-change slab, one side of which is isothermal while the other is insulated, is considered. Both cases—fusion and solidification—are treated. Slab temperature at the intitial moment is assumed constant and not critical. The main goal of this paper is to find the additional time required for a total phase change, compared with the case of the critical initial temperature. By analogy with perturbation problems in hydrodynamics, an appropriate solution is constructed consisting of an inner and an outer solution. The evaluation of the maximum error of the integral heat balance equation of the slab is treated as an indirect evaluation of the accuracy of the solution obtained. This evaluation shows that the solution can provide sufficient accuracy only in cases in which at least one of the three nondimensional parameters of the problem is small.

scholarly journals Phase Change Enthalpies and Entropies of Liquid Crystals

2006 ◽  
Vol 35 (3) ◽  
pp. 1051-1330 ◽  
Author(s):  
William E. Acree ◽  
James S. Chickos
Keyword(s):  
Liquid Crystals ◽  
Phase Change
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