Dielectric studies. Part XXV. Methoxy group rotation in anisole and three para-substituted anisoles

1969 ◽  
Vol 47 (24) ◽  
pp. 4645-4650 ◽  
Author(s):  
D. B. Farmer ◽  
S. Walker
Keyword(s):  
Relaxation Process ◽  
Methoxy Group ◽  
Relaxation Times ◽  
Pure Liquid ◽  
Relaxation Processes ◽  
Molecular Relaxation ◽  
Microwave Frequencies ◽  
Dielectric Absorption ◽  
Weight Factors ◽  
Group Rotation

The dielectric absorption at several microwave frequencies of anisole, p-methylanisole, and p-bromoanisole in the solvent p-xylene, and p-dimethoxybenzene in the solvent cyclohexane has been investigated at 4 to 6 temperatures. Anisole, p-methylanisole, and p-dimethoxybenzene were all found to relax mainly by methoxy group rotation, whereas the relaxation process in p-bromoanisole was very largely molecular relaxation. In the literature, considerable divergence exists for the analyses of the dielectric data of anisole and substituted anisoles into contributions from two relaxation times and the magnitude of the weight factors governing each relaxation process. Such divergencies have been explored and justifiable analyses established for these systems where the weight factors governing the relaxation processes are shown to be roughly of the same order as those estimated from group moment data. The weight factor for molecular relaxation in the pure liquid appears considerably greater than that for a dilute solution of it in a non-polar solvent.

Dielectric studies. Part XVII. Relaxation processes and corresponding enthalpies of activation of some mono-substituted benzenes

1968 ◽  
Vol 46 (6) ◽  
pp. 841-845 ◽  
Author(s):  
J. Crossley ◽  
S. Walker
Keyword(s):  
Relaxation Times ◽  
Molecular Size ◽  
Relaxation Processes ◽  
Dielectric Studies ◽  
Molecular Reorientation ◽  
Substituted Benzenes ◽  
Microwave Frequencies ◽  
Dielectric Absorption ◽  
Expected Increase ◽  
Xylene Solution

The dielectric absorption at several microwave frequencies of liquid ethylbenzene, isopropylbenzene, and phenyltrimethylsilane at 15, 37.5, and 50 °C and cyclohexane solutions of t-butylbenzene and benzotrichloride at 15, 37.5, 45, and 50 °C has been examined. Benzotrichloride has also been studied in cyclohexane and p-xylene solution at 25 °C. Only molecular reorientation can be detected for benzotrichloride, whereas the remainder are all characterized by an absorption that may be analyzed into two relaxation times, one associated with molecular reorientation (τ1) and a shorter relaxation time (τ2) which appears to be attributable to an intermolecular process. The enthalpies of activation of the τ1 process show the expected increase with increasing molecular size, while no temperature dependence is detectable for the shorter relaxation process.

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.

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.

Relaxation processes of quinoline, isoquinoline, and their mixtures

1980 ◽  
Vol 58 (1) ◽  
pp. 20-24 ◽  
Author(s):  
M. P. Madan
Keyword(s):  
Thermodynamic Parameters ◽  
Molecular Motion ◽  
Polar Solvent ◽  
Relaxation Times ◽  
Relaxation Processes ◽  
Polar Components ◽  
Dielectric Absorption ◽  
System A ◽  
Dielectric Data ◽  
Activated State

The dielectric absorption of quinoline, isoquinoline, and their binary mixtures has been studied in the microwave region over a range of temperatures in dilute benzene and n-heptane solutions. The relaxation times and the thermodynamic parameters for the activated state have been determined using the measured dielectric data. The results obtained have been discussed in terms of the molecular motion of the system. A relation has been proposed to represent the relaxation behavior of a system of two Debye-type polar components in a non-polar solvent. The relation has been tested by comparing the calculated values with those determined experimentally for a few systems consisting of similar, simple rigid polar molecules.

scholarly journals The Dynamic Properties of 5Cb Filled with Aerosil Particles Investigated by Pcs

1999 ◽  
Vol 559 ◽  
Author(s):  
F.M. Aliev ◽  
M. Kreuzer ◽  
Yu.P. Panarin
Keyword(s):  
Liquid Crystal ◽  
Temperature Dependence ◽  
Relaxation Process ◽  
Nematic Liquid Crystal ◽  
Broad Spectrum ◽  
Dynamic Properties ◽  
Relaxation Times ◽  
Correlation Spectroscopy ◽  
Relaxation Processes ◽  
Optoelectronic Application

ABSTRACTNematic liquid crystal filled with Aerosil particles, a prospective composite material for optoelectronic application, has been investigated by static light scattering and Photon Correlation Spectroscopy (PCS). The Aerosil particles in filled nematic liquid crystals (FN) form a network structure with LC domains about 2500 Å in size with a random distribution of the director orientation of each domain.We found that the properties of 5CB are considerably affected by the network. The N-I phase transition in filled 5CB was found to be smeared out and depressed. PCS experiments show that two new relaxation processes appear in filled 5CB in addition to the director fluctuation process in bulk. The slow relaxation process, with a broad spectrum of relaxation times, is somewhat similar to the slow decay, which is observed in confined nematic liquid crystal.The middle frequency process was assigned to the director fluctuations in the surface layer formed at the particle-LC interface. The decay function describing this relaxation process is a stretched exponential (β ≍ 0.7). The temperature dependence of the relaxation times of the middle frequency obeys the Vogel-Rilcher law. Such a temperature dependence, accompanied by a broad spectrum of relaxation times suggests that the dynamics of the director fluctuations near the Aerosil particle-LC interface is glass-like.

Dielectric Dispersion Studies of Some Intramolecular Hydrogen Bonded Molecules at Microwave Frequencies

1977 ◽  
Vol 32 (6) ◽  
pp. 604-606 ◽  
Author(s):  
H. D. Purohit ◽  
S. Kumar ◽  
A. D. Vyas
Keyword(s):  
Dielectric Loss ◽  
Complex Plane ◽  
Dipole Moments ◽  
Dielectric Dispersion ◽  
Dielectric Relaxation Time ◽  
Relaxation Processes ◽  
Microwave Frequencies ◽  
Group Rotation ◽  
Intramolecular Hydrogen ◽  
Straight Lines

Abstract The permittivity and dielectric loss of acetyl acetone, benzoyl acetone and dibenzoyl methane have been measured at four microwave frequencies viz., 30.20, 24.50, 18.26, and 9.83 GHz and also at 1 MHz and optical frequency at 35 °C. The permittivity and dielectric loss at different frequen­ cies have been plotted against concentration (wt. fraction). The slopes of these straight lines have been used for the complex plane plots (a″ vs. a′). The complex plane plots for these compounds are Cole-Cole arcs. The dielectric relaxation time (τ0) and distribution parameter (α) have been calculated from these plots. Data have been analysed in terms of two relaxation processes i. e., cor­ responding to overall rotation and group rotation. The dipole moments of these molecules are reported.

Dielectric relaxation of acetyl- and benzoyl-acetones

1989 ◽  
Vol 67 (5) ◽  
pp. 804-808 ◽  
Author(s):  
R. K. Khanna ◽  
Abha Bhatnagar
Keyword(s):  
Dielectric Relaxation ◽  
Dipole Moments ◽  
Relaxation Times ◽  
Weight Fraction ◽  
Relaxation Mechanism ◽  
Relaxation Processes ◽  
Dielectric Absorption ◽  
Molar Polarization ◽  
Distribution Parameters ◽  
Few Data

Dielectric absorption measurements are reported at radio and microwave frequencies (at six different wavelengths) for acetylacetone and benzoylacetone solutions in benzene, in a temperature range 25–60 °C. Analysis of dielectric data in terms of Cole–Cole arc plots and multiple relaxation processes reveals that, at higher temperatures, overall molecular relaxation is the dominant relaxation mechanism in these β-diketones. The observed relaxation times, distribution parameters, and dipole moments are in reasonable agreement with the few data reported for some temperatures, in the literature. The activation energy parameters are also evaluated assuming dielectric relaxation to be a rate process. Molar polarization vs. weight fraction (concentration) plots show anomalous behaviour for acetylacetone. Keywords: dielectric properties, dielectric losses, relaxation times, dipole moment, dielectric absorption and dispersion, microwave measurements.

Dielectric dispersion and relaxation mechanism in some trichloro esters at microwave frequencies

1977 ◽  
Vol 55 (21) ◽  
pp. 1902-1905 ◽  
Author(s):  
H. D. Purohit ◽  
H. S. Sharma ◽  
A. D. Vyas
Keyword(s):  
Relaxation Time ◽  
Dielectric Loss ◽  
Weight Fraction ◽  
Relaxation Mechanism ◽  
Dielectric Dispersion ◽  
Relaxation Processes ◽  
Optical Frequency ◽  
Microwave Frequencies ◽  
Group Rotation ◽  
Straight Lines

The permittivity and dielectric loss of three trichloro esters, namely methyl trichloroacetate, ethyl trichloroacetate, and n-propyl trichloroacetate have been measured at frequencies 1 MHz, 9.83, 18.26, 24.50 GHz, and optical frequency at 35 °C. The permittivity and dielectric loss at different frequencies have been plotted against concentration (weight fraction). The slopes of these straight lines have been used for complex plane plots (a″ vs. a′). There are two possible relaxation processes in these molecules, i.e. overall rotation of the molecule and intramolecular group rotation —CCl3 around C—C bond. Whereas the relaxation time for overall rotation is dependent on temperature the relaxation time for group rotation is practically independent of temperature.

Molecular Relaxation Processes in Nucleic Acids Components as Probed with Raman Spectroscopy

2017 ◽  
Vol 68 (10) ◽  
Author(s):  
Cristina M. Muntean ◽  
Ioan Bratu ◽  
Carmen Tripon ◽  
Konstantinos Nalpantidis ◽  
Monica A. P. Purcaru ◽  
...  
Keyword(s):  
Nucleic Acids ◽  
Solid Phase ◽  
Dynamical Behavior ◽  
Relaxation Times ◽  
Relaxation Mechanism ◽  
Disodium Salt ◽  
Relaxation Processes ◽  
Molecular Relaxation ◽  
Salt Hydrate ◽  
Dna And Rna

In this work the Raman total half bandwidths of five free nucleic acids components (cytidine-5`- monophosphate, 2`- deoxycytidine 5`- monophosphate, 2`- deoxyguanosine-5`- monophosphate, thymidine - 5� - monophosphate disodium salt hydrate and uridine-5`- monophosphate disodium salt) have been measured, respectively. Raman scattering can be used to study the fast molecular relaxation processes of free nucleic acids components in solid phase. The dependencies of the total half bandwidths and of the corresponding global relaxation times, on functional groups and on the type of DNA and RNA constituents, are reported. In our study, the full widths at half-maximum (FWHMs) for the Raman bands of these nucleic acids components, are typically in the wavenumber range from 9 to 28 cm-1. Besides, it can be observed that the (sub)picosecond dynamics studied in this work, has a global relaxation time value smaller than 1.18 ps and larger than 0.38 ps. We have found that the band centered at 1264 cm-1 for cytidine -5`- monophosphate, the profile near 1373 cm-1 attributed to thymidine -5`- monophosphate disodium salt hydrate and the band around 1233 cm-1 attributed to uridine -5`- monophosphate disodium salt, respectively, are suitable for studying the dynamical behavior of molecular fragments in nucleic acids components. For the case of solid phase samples of nucleic acids components, we can suppose that the dominant relaxation mechanism is of the vibrational type one.

Intramolecular Rotation in Some Trihalogenated Esters at Microwave Frequencies

1978 ◽  
Vol 33 (2) ◽  
pp. 232-234 ◽  
Author(s):  
H. D. Purohit ◽  
A. D. Vyas ◽  
H. C. Lunker
Keyword(s):  
Dielectric Loss ◽  
Complex Plane ◽  
Dispersion Curves ◽  
Relaxation Processes ◽  
Optical Frequency ◽  
Methyl Ethyl ◽  
Microwave Frequencies ◽  
Group Rotation ◽  
Straight Lines ◽  
Intramolecular Rotation

The permittivity and dielectric loss of methyl, ethyl and n-propyl trichloroacetate in decalin solution have been measured at four microwave frequencies viz., 30.20, 24.50, 18.26 and 9.83 GHz and also at 1 MHz and optical frequency at 35 °C. The permittivity and dielectric loss at different frequencies have been plotted against concentration (wt. fraction). The slopes of these straight lines have been used for complex plane plots (a″ vs a′). The dispersion curves which could not be resolved in benzene could be resolved in decalin due to the increase in viscosity of the solvent. Data have been analysed in terms of two relaxation processes i.e., overall rotation and group rotation.

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