The dielectric constant of a liquid

1953 ◽  
Vol 6 (2) ◽  
pp. 93 ◽  
Author(s):  
AD Buckingham
Keyword(s):  
Dielectric Constant ◽  
Dipole Moment ◽  
Polar Solvent ◽  
Molecular Model ◽  
Principal Direction ◽  
Molecular Shape ◽  
Pure Liquid ◽  
Dilute Solution ◽  
Onsager Theory ◽  
Special Case

Some earlier theories in which attempts have been made to allow for the influence of molecular shape on the static dielectric constant of a liquid are shown to be inaccurate. A general equation is derived for the dielectric constant of a liquid, and this is then applied to a molecular model consisting, in the first instance, of an ellipsoid uniformly polarized in a principal direction, and secondly, to an optically anisotropic ellipsoid ; in both cases the surroundings are assumed to form a continuum. The results of this more general approach applied to several substances are more satisfactory than those obtained by the original Onsager theory. The theory is also applied to mixtures, and in the special case of a dilute solution in a non-polar solvent, the equation of Ross and Sack is obtained when the ellipsoid is isotropic. A correlation has been noted in the discrepancies found when the dipole moment of a substance is calculated by means of observations on the pure liquid and on dilute solutions in a non-polar solvent, using the equations derived in the present paper.

π-Elektronen-Dipolmoment eines Pyridinium-N-phenol-betains

1966 ◽  
Vol 21 (9) ◽  
pp. 1373-1376 ◽  
Author(s):  
A. Schweig ◽  
C. Reichardt
Keyword(s):  
Dielectric Constant ◽  
Dipole Moment ◽  
Ground State ◽  
Dipole Moments ◽  
Saturated Hydrocarbon ◽  
Dilute Solution ◽  
Uniform Medium ◽  
Order Of Magnitude ◽  
Dimensional Electron Gas ◽  
Experimental Values

The ground state dipole moment of the π-electrons of 2.4.6-triphenyl-N- [3.5-di-tert-butyl-4-hydroxy-phenyl] -pyridinium-betain I, a highly solvatochromic substance, was determined by measuring the dielectric constant of a dilute solution and calculating first the dipole moment of the whole system (σ- and π-electrons) using the method of HALVERSTADT and KUMLER. The dipole moment of the π-electrons was then calculated, asuming the π-electron dipole to be imbedded in a spherical medium of dielectric constant 2. The value calculated by this method was compared with the π-electron dipole moment directly obtained from the dielectric constant of the dilute solution using a method of H. KUHN. This method is based on the assumption that a π-electron of a dissolved molecule sees the σ-electrons of the molecule and of the surrounding solvent, a saturated hydrocarbon, as a continuous uniform medium of dielectric constant 2. Thus the π-electron dipole of the solute molecule is regarded as being imbedded in a continuous medium of dielectric constant 2. It was found that the values of the π-electron dipole moments determined by the two methods agree well. Furthermore these experimental values agree with a theoretical value obtained in the case of N- [4-hydroxy-phenyl] -pyridinium-betain II using the one dimensional electron gas method including electron repulsion. The order of magnitude of the π-electron dipole moment of I clearly shows that the ground state of this molecule is highly polar.

scholarly journals FOLDING ELASTIC TRANSMEMBRANE HELICES TO FIT IN A LOW-RESOLUTION IMAGE BY ELECTRON MICROSCOPY

2011 ◽  
Vol 09 (supp01) ◽  
pp. 37-50 ◽  
Author(s):  
YUTAKA UENO ◽  
KAZUNORI KAWASAKI ◽  
OSAMU SAITO ◽  
MASAFUMI ARAI ◽  
MAKIKO SUWA
Keyword(s):  
Membrane Proteins ◽  
Structure Prediction ◽  
Molecular Model ◽  
Imaging Techniques ◽  
Transmembrane Helix ◽  
Prediction Method ◽  
Molecular Shape ◽  
Coarse Grained ◽  
Transmembrane Helices ◽  
Low Resolution

Structure prediction of membrane proteins could be constrained and thereby improved by introducing data of the observed molecular shape. We studied a coarse-grained molecular model that relied on residue-based dummy atoms to fold the transmembrane helices of a protein in the observed molecular shape. Based on the inter-residue potential, the α-helices were folded to contact each other in a simulated annealing protocol to search optimized conformation. Fitting the model into a three-dimensional volume was tested for proteins with known structures and resulted in a fairly reasonable arrangement of helices. In addition, the constraint to the packing transmembrane helix with the two-dimensional region was tested and found to work as a very similar folding guide. The obtained models nicely represented α-helices with the desired slight bend. Our structure prediction method for membrane proteins well demonstrated reasonable folding results using a low-resolution structural constraint introduced from recent cell-surface imaging techniques.

Temperaturabhängigkeit der statischen Dielektrizitätskonstante und des optischen Brechungsindexes von Flüssigkeiten

1975 ◽  
Vol 30 (3) ◽  
pp. 287-291 ◽  
Author(s):  
I. Gryczyński ◽  
A. Kawski
Keyword(s):  
Dielectric Constant ◽  
Refractive Index ◽  
Dipole Moment ◽  
Dipole Moments ◽  
Mixed Solvents ◽  
Temperature Changes ◽  
Temperature Dependences ◽  
Solvent Shifts ◽  
Pure And Mixed Solvents ◽  
Good Agreement

A variation of the temperature changes the static dielectric constant (ε) and the refractive index (n) of solvents and, in conjunction with the measurement of solvent shifts of absorption and fluorescence maxima, allows the investigation of dipole moment changes of solutes in the excited state. For this purpose, investigations of the temperature dependences of ε and n of some pure and mixed solvents of different polarities have been made. It is found that the excited dipole moments of indole, 1,2-dimethylindole, 2,3-dimethylindole and tryptophan obtained from the shifts of the fluorescence maxima in mixed solvents at high temperatures are in good agreement with those obtained in other ways.

Bromine Pentafluoride. The Electric Dipole Moment in the Vapor State and the Dielectric Constant of the Liquid1

1956 ◽  
Vol 78 (1) ◽  
pp. 44-45 ◽  
Author(s):  
Max T. Rogers ◽  
Richard D. Pruett ◽  
H. Bradford Thompson ◽  
John L. Speirs
Keyword(s):  
Dielectric Constant ◽  
Dipole Moment ◽  
Electric Dipole Moment ◽  
Electric Dipole ◽  
Vapor State

Dielectric constant and dipole moment of hydrofluorocarbon refrigerant mixtures R404A, R407C, and R507

2000 ◽  
Vol 32 (6) ◽  
pp. 631-651 ◽  
Author(s):  
Filipe de Brito ◽  
Anelia Gurova ◽  
Carlos Nieto de Castro ◽  
Umesh Mardolcar
Keyword(s):  
Dielectric Constant ◽  
Dipole Moment ◽  
Refrigerant Mixtures

Détermination de propriétés diélectriques de substances polaires: conditions d'applicabilité de l'équation d'Omini

1982 ◽  
Vol 60 (18) ◽  
pp. 2398-2402
Author(s):  
Léo Dégrève ◽  
Paulo Roberto Brossi Pelissari ◽  
Maria Marcia Murta
Keyword(s):  
Dielectric Constant ◽  
Dipole Moment ◽  
Nonpolar Solvents

An equation which allows for the determination of the dipole moment and polarizability of polar substances via the dielectric constant of solutions of the substance in nonpolar solvents is tested using different solute–solvent pairs. The results indicate that this equation provides good values of the dipole moment and of the polarizability if the solvent is correctly chosen. [Journal translation]

Sign in / Sign up

Export Citation Format

Share Document