Dielectric studies. Part XX. Molecular relaxation of some heterocyclic amines in dilute solution

1968 ◽  
Vol 46 (14) ◽  
pp. 2369-2372 ◽  
Author(s):  
J. Crossley ◽  
S. Walker
Keyword(s):  
Relaxation Time ◽  
Dipole Moments ◽  
Relaxation Times ◽  
Lone Pair ◽  
Intermolecular Forces ◽  
Dilute Solution ◽  
Microwave Frequencies ◽  
Heterocyclic Molecules ◽  
Dielectric Constant And Loss ◽  
The Difference

Dielectric constant and loss data have been obtained at microwave frequencies for acridine, 4-methyl-pyridine, phthalazine, quinoline, and isoquinoline in both cyclohexane and p-xylene solution. The data have been used to calculate relaxation times and apparent dipole moments. For phthalazine, quinoline, and isoquinoline in cyclohexane at 50 °C the distribution coefficient is zero and their relaxation times are very similar. Although the axes about which these three molecules may relax lead to different volumes being swept out, no variation in relaxation behavior has been detected, and each system can be characterized by one relaxation time. The relaxation times for all the heterocyclic molecules except quinoline and acridine in p-xylene are appreciably longer than in cyclohexane. Relaxation time values appear a sensitive means of detecting the weak molecular interaction between the amine and the p-xylene. The difference in behavior between the quinoline and acridine as opposed to isoquinoline could be attributed to a more appreciable steric effect in the former two, hindering the approach of the π-electrons of the p-xylene molecules to the hybridized lone pair on the nitrogen atom. No interaction is, in fact, detectable in the case of quinoline and acridine. The importance of allowing for weak intermolecular forces, even in dilute solution, when relaxation values are being anticipated, is emphasized.

Dipole moment and dielectric relaxation studies in some azo compounds

1982 ◽  
Vol 60 (2) ◽  
pp. 257-260 ◽  
Author(s):  
P. B. K. Sarma ◽  
P. V. G. K. Murthy ◽  
C. R. K. Murty
Keyword(s):  
Dipole Moment ◽  
Solution Method ◽  
Dipole Moments ◽  
Relaxation Times ◽  
Azo Compounds ◽  
Dielectric Anisotropy ◽  
Dilute Solution ◽  
Microwave Frequencies ◽  
Central Group ◽  
Relaxation Studies

Dipole moments (μ) and relaxation times (τ) of seven azo central group liquid crystal compounds have been determined using the dilute solution method at radio and microwave frequencies. The results agree fairly well with the estimated values of the dipole moments. The angle, β, between the direction of the dipole moment and the long axis of the molecule, is determined for each molecule from structural considerations. The predicted sign of the dielectric anisotropy (Δε) from the estimated value of p is confirmed experimentally.

Dielectric studies. Part XVIII. Dipole moments and relaxation times of some symmetrically substituted alkylbenzenes

1968 ◽  
Vol 46 (6) ◽  
pp. 847-851 ◽  
Author(s):  
J. Crossley ◽  
S. Walker
Keyword(s):  
Relaxation Time ◽  
Dipole Moments ◽  
Relaxation Times ◽  
Pure Liquid ◽  
Dielectric Studies ◽  
Molecular Reorientation ◽  
Microwave Frequencies ◽  
Short Relaxation Time ◽  
Dielectric Absorption ◽  
Liquid Benzene

The dielectric absorption at four microwave frequencies of pure liquid benzene and p-cymene at 25 °C, p-xylene and mesitylene at 25, 40, 50, and 60 °C, and solutions of durene and hexamethylbenzene in mesitylene at 60 °C has been examined. All show measurable loss factors and apparent dipole moments of about 0.1 to 0.2 D. These moments are less in magnitude than those associated with the short relaxation time (τ2) process for the polar monoalkylbenzenes. o-xylene and m-xylene. Their relaxation times are too short for molecular reorientation and there is a rough correlation between the number of collisions/molecule s and the reciprocal relaxation time.

A Cavity Perturbation Technique for Measuring Complex Dielectric Permittivities of Liquids at Microwave Frequencies

1974 ◽  
Vol 52 (23) ◽  
pp. 2365-2369 ◽  
Author(s):  
Abhai Mansingh ◽  
D. B. McLay ◽  
K. O. Lim
Keyword(s):  
Dielectric Constant ◽  
Benzene Solution ◽  
Dipole Moments ◽  
Perturbation Technique ◽  
Relaxation Times ◽  
Microwave Frequencies ◽  
Dielectric Constant And Loss ◽  
End Caps ◽  
Good Agreement

A microwave technique for measuring the complex dielectric permittivity of liquids by using a cylindrical cavity oscillating in the TM010 mode is described. The liquid is placed in a cylindrical teflon cell and the dielectric constant and loss of the liquid are evaluated by measuring accurately the changes in the resonant frequency and Q of the cavity for the composite sample and for the teflon alone. This technique has been used to measure the dielectric constant and loss at 2.4 GHz of some pure liquids and solutions in benzene of ortho and meta isomers of difluoro-, dichloro-, dibromo-, and diiodo-benzene. The measured values for the pure liquids are in good agreement with the literature values. The dielectric relaxation times and dipole moments of the dihalobenzenes in benzene solution evaluated by assuming a simple Debye type dispersion show good agreement with the earlier calculated values derived from Cole–Cole plots based on measurements at several microwave frequencies. This technique, by virtue of the use of a teflon cell and of gold plated end caps, allows the determination of the dielectric properties of corrosive liquids at microwave frequencies and another advantage is that very small liquid samples are required.

Magnetic Resonance Relaxation Characteristics of Muscle, Fat and Bone Marrow of the Extremities

1987 ◽  
Vol 28 (3) ◽  
pp. 363-364 ◽  
Author(s):  
H. Pettersson ◽  
R. Slone
Keyword(s):  
Bone Marrow ◽  
Relaxation Time ◽  
Magnetic Resonance ◽  
Normal Values ◽  
Subcutaneous Fat ◽  
Relaxation Times ◽  
T2 Relaxation ◽  
The Difference ◽  
Resonance Relaxation ◽  
Relaxation Characteristics

The T1 and T2 relaxation times were calculated in the bone marrow, subcutaneous fat and muscles in the extremities of 21 volunteers. There were no significant differences in relation to age or sex. In the same individual, the difference in the relaxation time was negligible between different sites in muscle, fat and bone. These and other normal values reported are dependent on examination technique and calculation method which must be compensated for when comparisons between materials from different centers are performed.

Dielectric Relaxation of Bromoalkanes in Cyclohexane Solution

1972 ◽  
Vol 50 (13) ◽  
pp. 2031-2034 ◽  
Author(s):  
Sing Pin Tay ◽  
John Crossley
Keyword(s):  
Dielectric Constant ◽  
Dielectric Relaxation ◽  
Dipole Moments ◽  
Relaxation Times ◽  
Dielectric Constant And Loss ◽  
Distribution Parameters

Mean relaxation times, Cole–Cole distribution parameters and apparent dipole moments, obtained from dielectric constant and loss measurements at 2 MHz and 1.5, 2.0, 2.5, 9.3, 16, 24, 35, 70, and 145 GHz, are reported for 1-, 2-, and 4-bromooctane, 1-bromodecane, 1-bromododecane, 1-bromohexadecane, 1-bromooctadecane, and 1,10-dibromodecane in cyclohexane solution at 25 °C.

The dielectric relaxation of some diols in p-dioxane solution

1978 ◽  
Vol 56 (3) ◽  
pp. 352-354 ◽  
Author(s):  
J. Crossley
Keyword(s):  
Dielectric Constant ◽  
Dielectric Relaxation ◽  
Relaxation Process ◽  
Alkyl Group ◽  
Relaxation Times ◽  
Dielectric Dispersion ◽  
Dioxane Solution ◽  
Microwave Frequencies ◽  
Dielectric Absorption ◽  
Dielectric Constant And Loss

Dielectric constant and loss data at up to nine microwave frequencies have been obtained for 1-butanol, 1,4-butanediol, 1,7-heptanediol, 1,8-octanediol, 1,10-decanediol, and 1,12-do-decanediol at 25 °C, and for 1,6-hexanediol at 15, 25, 40, and 55 °C, in p-dioxane. In each case the dielectric dispersion is adequately described by a Cole-Cole distribution. The relaxation times for the diols are almost independent of the length of the alkyl group. An intramolecular relaxation process appears to be primarily responsible for the dielectric absorption.

Microwave absorption and dielectric relaxation of some rigid molecules and their mixtures

1977 ◽  
Vol 55 (10) ◽  
pp. 878-883 ◽  
Author(s):  
M. P. Madan ◽  
M. Shelfoon ◽  
I. Cameron
Keyword(s):  
Dielectric Constant ◽  
Relaxation Time ◽  
Loss Factor ◽  
Relaxation Times ◽  
Liquid Mixtures ◽  
Polar Component ◽  
Simple Liquid ◽  
Dielectric Data ◽  
Dielectric Constant And Loss ◽  
Activated State

The dielectric constant and loss factor of some rigid molecules, pyridine, quinoline, and isoquinoline, and their mixtures have been measured in dilute benzene solutions in the microwave region over a range of temperatures. The dielectric data have been used to determine the relaxation times and the thermodynamic parameters for the activated state. The values of the relaxation time for single polar component solutions agree well at temperatures at which there are available known data. The relaxation times for the mixtures are consistent with the results on simple liquid mixtures of polar molecules in dilute solutions which were previously studied by us and by some other workers.

Dielektrische Relaxation von aliphatischen Kettenmolekülen mit endständigen Halogen-Gruppen in verdünnter Lösung / Dielectric Relaxation of α, ω-Halogen Alkanes in Dilute Solution

1975 ◽  
Vol 30 (11) ◽  
pp. 1403-1412 ◽  
Author(s):  
G. Klages ◽  
M. Straßmann
Keyword(s):  
Relaxation Time ◽  
Chain Length ◽  
Time Distribution ◽  
Dipole Moments ◽  
Low Frequency ◽  
Aliphatic Chain ◽  
Dilute Solution ◽  
Relaxation Time Distribution ◽  
Absorption Region ◽  
Chain Molecules

Dielectric loss in the 0.3 to 140 GHz range, and to some extent dispersion, of seven selected aliphatic chain molecules, substituted by Cl, Br, and I at both ends have been measured in dilute solutions of n-heptane, benzene, and decalin. Chain length varied from 3 to 10 carbon atoms. For 1,10-dichlorodecane in decalin and mesitylene the temperature was also varied from -30 to + 60 °C. The unsymmetric absorption curves have been resolved in a weak FIR region and a predominant region with a symmetric relaxation time distribution (log. scale) according to Fröhlich. The width of this distribution is shown to be independent of chain length and halogen. Its mean relaxation time increases linearly with chain length, while the dipole moment goes through a minimum for the butyl compounds.Monoderivatives, three chlorides and one bromide, have also been measured in the same solvents at 20 °C. Their absorption curves can be fitted by a predominant absorption region with the same width as for the corresponding di-derivatives and, besides the FIR wing, by another low frequency Debye-region, the weight of which decreases with increasing chain length. The molecular motions related to these three regions are discussed, and the corresponding magnitudes of dipole moments in mono- and di-derivatives are compared for long and short chains

Dielektrische Absorption von Alkoholen und Phenolen in verdünnter Lösung bei Mikro- und Sub-mm-Wellen / Dielectric Absorption of Microwaves and Submillimeterwaves by Alcohols and Phenols in Dilute Solution

1977 ◽  
Vol 32 (12) ◽  
pp. 1512-1520
Author(s):  
A. Camacho Beitrán ◽  
G. Klages
Keyword(s):  
Relaxation Time ◽  
Relaxation Times ◽  
Hydroxyl Group ◽  
Dilute Solution ◽  
Aromatic Solvent ◽  
Dielectric Absorption ◽  
First Approximation ◽  
Wave Region ◽  
Wave Range ◽  
Solvent Molecules

Abstract Dielectric Absorption of Microwaves and Submillimeterwaves by Alcohols and Phenols in Dilute Solution Dielectric lossers of benzylaleohol, cyclohexanol, n-decanol, and diphenylcarbinol and also of phenol, p-cresol, 2,4,6-trimethylphenoI and diphenylether have been measured over the 1 to 300 GHz frequency band using aliphatic and aromatic solvents. In cyclohexane solutions, measurements have also been made at two frequencies in the sub-mm-wave range. From an analysis of the absorption curves a distribution of relaxation times is obtained in a first approximation. Comparing the results from 3 alcohols and 3 phenols, differences are found between the relaxation time of the hydroxyl group and the live time of hydrogen bonds to aromatic solvent molecules. More than one relaxation time is found in diphenylether and its absorption curve in cyclohexane has a slope steeper than a Debye curve in the sub-mm-wave region, which is discussed as inertial effect.

Dielectric Relaxation of Alkyl Acetates in Aromatic and Aliphatic Solvents at Microwave Frequencies

1972 ◽  
Vol 50 (13) ◽  
pp. 1449-1452 ◽  
Author(s):  
G. P. Srivastava ◽  
P. C. Mathur ◽  
Mrs. Krishna
Keyword(s):  
Dielectric Relaxation ◽  
Dipole Moments ◽  
Relaxation Times ◽  
Strong Interactions ◽  
Dielectric Relaxation Time ◽  
Methyl Ethyl ◽  
Microwave Frequencies ◽  
Aromatic Solvents ◽  
Nonpolar Solvents ◽  
Alkyl Acetates

The dielectric relaxation times and the dipole moments of methyl, ethyl, and amyl acetates are measured in six nonpolar solvents having different viscosities. The dielectric relaxation time is found to increase with the chain length in each nonpolar solvent. The relaxation times in aromatic solvents (benzene and p-xylene) are found to be higher than in carbon tetrachloride, even though the viscosity of the latter is more than that of the aromatic solvents This shows that the dielectric relaxation is not only due to the viscous resistance of the solvent but is also influenced by strong interactions between aromatic solvents and solute molecules.

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