Dielectric relaxation in 2-acetylnaphthalene and related compounds

1978 ◽  
Vol 56 (4) ◽  
pp. 567-573 ◽  
Author(s):  
J. Crossley ◽  
M. A. Mazid ◽  
C. K. McLellan ◽  
P. F. Mountain ◽  
S. Walker
Keyword(s):  
Activation Parameters ◽  
Low Frequencies ◽  
Microwave Frequencies ◽  
Dielectric Absorption ◽  
Free Energy Of Activation ◽  
Polystyrene Matrix ◽  
The Matrix ◽  
Acetyl Group ◽  
Related Compounds ◽  
Xylene Solution

The dielectric absorption of 2-acetylnaphthalene and 2- and 3-acetylphenanthrene has been studied in p-xylene solution at several microwave frequencies and in a polystyrene matrix at low frequencies. Acetyl group relaxation has been established from both sets of data. A clear separation of the dielectric absorption of the molecule and the group has been achieved for both 2- and 3-acetylphenanthrene in the matrix. The Eyring activation parameters have been established for acetyl relaxation in these molecules in the matrix. The free energy of activation values for group relaxation increase in the sequence acetophenone < 2-acetylphenanthrene < 3-acetylphenanthrene < 2-acetylnaphthalene. For the p-xylene solution data the weight factor for group relaxation, C2, is appreciably lower than the theoretical value, so that C2 < C1, bearing out the findings of Fong and Smyth for 2-acetylnaphthalene. In polystyrene matrices, the data for 2- and 3-acetylphenanthrene also indicated that C2 < C1. The enthalpy of activation for acetyl relaxation in 2- and 3-acetylphenanthrene is similar to that for acetophenone and 1,4-diacetylbenzene whereas that for 2-acetylnaphthalene would seem somewhat larger.

Acetyl group relaxation in four aromatic ketones

1977 ◽  
Vol 55 (4) ◽  
pp. 583-587 ◽  
Author(s):  
C. K. McLellan ◽  
S. Walker
Keyword(s):  
Energy Barrier ◽  
Benzene Solution ◽  
Far Infrared ◽  
Aromatic Ketones ◽  
Dielectric Absorption ◽  
Nmr Data ◽  
Polystyrene Matrix ◽  
Absorption Studies ◽  
Acetyl Group ◽  
Experimental Errors

Dielectric absorption studies have been made of group relaxation of acetophenone, 1,4-diacetylbenzene,4-acetylbiphenyl, and 2-acetylfluorene in a polystyrene matrix, and two rigid molecules have also been examined. For acetyl group relaxation in acetophenone, ΔHE = 29.6 ± 0.6 kJ mol−1 and ΔSE = 26 ± 3 JK−1 mol−1 (95% confidence intervals). The energy barrier for acetyl group relaxation is of the same order as that obtained from nmr data. Our results for acetophenone differ appreciably from the values reported for the gaseous phase by the far-infrared approach and from those by the dielectric absorption of aromatic ketones in benzene solution. The enthalpies of activation for acetyl group relaxation in 1,4-diacetylbenzene, 4-acetylbiphenyl, and 2-acetylfluorene are 29, 30, and 32 kJ mol−1, respectively, which values are identical within their experimental errors. These three substances have also been examined as pure solids, yielding enthalpies of activation for acetyl group relaxation of a similar magnitude.

Molecular and group relaxation studies in parasubstituted benzenes in various media

1979 ◽  
Vol 57 (21) ◽  
pp. 2843-2847 ◽  
Author(s):  
J. Crossley ◽  
J. P. Shukla ◽  
S. P. Tay ◽  
M. S. Walker ◽  
S. Walker
Keyword(s):  
Group Process ◽  
Activation Enthalpy ◽  
Small Contribution ◽  
Molecular Processes ◽  
Dielectric Absorption ◽  
Polystyrene Matrix ◽  
Absorption Studies ◽  
The Matrix ◽  
Intramolecular Motion ◽  
Relaxation Studies

Dielectric absorption studies have been made on molecules of the type [Formula: see text][Formula: see text] where X—Y is —OCH3, —COCH3, —CH2Cl, and —CH2CN. The molecules have been dissolved in (a) a polystyrene matrix and (b) in the viscous liquid o-terphenyl. For 1,4-dimethoxybenzene the group process dominates in both media, and estimates have been made of the activation enthalpy for group relaxation. For 1,4-dimethoxybenzene in benzene, decalin, Nujol, and o-terphenyl solutions, however, there appears to be a small contribution from the molecular process. No such contribution was detected in the matrix studies on this solute molecule. For 1,4-diacetylbenzene, 1,4-bis(chloromethyl)benzene, and 1,4-bis(cyanomethyl)benzene in o-terphenyl solution it again seems that the group and molecular processes overlap. However, in polystyrene the enthalpies of activation which emerge are characteristic of the group relaxation process as determined by the nmr approach. Altogether, the work illustrates that o-terphenyl may be a useful solvent in helping to decide whether a solute has contributions from an intramolecular motion.

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.

Methine bases in the benzothiazole, benzoselenazole, and quinoline series, and geometry and conformational preferences of their acyl derivatives

1995 ◽  
Vol 73 (8) ◽  
pp. 1278-1286 ◽  
Author(s):  
Ajay K. Gupta ◽  
Ali Ben-Mahmud ◽  
Lisa J. Kamphuis ◽  
Jennifer L. Mueller ◽  
Suzie S. Rigby ◽  
...  
Keyword(s):  
Aqueous Sodium Hydroxide ◽  
Difference Spectra ◽  
Molecular Mechanics Calculations ◽  
Dielectric Absorption ◽  
Quinoline Series ◽  
Conformational Preferences ◽  
Acetyl Group ◽  
Text Interaction ◽  
Related Compounds ◽  
Acyl Derivatives

Dimeric structures 2a–c are confirmed for the "methine bases" obtained from 2-methylbenzo-thiazolium and -selenazolium salts and aqueous sodium hydroxide, whereas monomeric structures 3 are confirmed for methine bases similarly derived from 2-methylquinolinium salts. The latter monomers dimerize slowly on standing. Monomeric methine bases 6–9, too hindered to dimerize, are described. 2-Acetonylidene-2,3-dihydro-3-methylbenzothiazole 10a and related compounds are assigned (Z) configurations on the basis of NOE difference spectra. Molecular mechanics calculations predict a slightly higher steric energy for the observed s-cis conformer of 10a than for the s-trans, indicating a stabilizing [Formula: see text] interaction in the s conformer that need only be a few kJ mol−1 in magnitude. For the quinolines 13a and b, the (E) configuration/s-cis conformation is favoured. The dielectric absorption method provides a rotational energy barrier of approximately 60 kJ mol−1 for acetyl group relaxation in 10a. Oxygen–sulfur exchange is observed in the conversion of 10a to 12a by thioacetic acid. Keywords: conformation, configuration, heterocyclic compounds, [Formula: see text] interaction.

Dielectric Studies. Part XXXI. Analysis of the Dielectric Data of Phenol and its Polymerized Forms

1971 ◽  
Vol 49 (7) ◽  
pp. 1106-1114 ◽  
Author(s):  
M. D. Magee ◽  
S. Walker
Keyword(s):  
Dipole Moment ◽  
Relaxation Time ◽  
Mole Fraction ◽  
The State ◽  
Distribution Parameter ◽  
Dielectric Studies ◽  
Microwave Frequencies ◽  
Dielectric Absorption ◽  
Dielectric Data ◽  
Intramolecular Process

The dielectric absorption and dispersions of several solutions of phenol in p-xylene have been measured at four microwave frequencies and at 2 MHz at a temperature of 25 °C. The data have been analyzed in terms of a mean relaxation time, a distribution parameter, and an apparent dipole moment which are useful empirical parameters for assessing the state of aggregation of the phenol molecules. The relaxation time at the lowest practicable concentration (0.02 mole fraction) is long for a molecule expected to relax predominantly by an intramolecular process. This and the behavior of the relaxation time and apparent dipole moment with increasing concentration are considered in terms of a model based on progressive association into an extended series of multimers, the trimer having a zero (or low) dipole moment and higher multimers becoming increasingly flexible.

scholarly journals Lithium Niobate Micro-transducers matrix design

2019 ◽  
Vol 281 ◽  
pp. 01001
Author(s):  
Hala El Rammouz ◽  
Farouk Benmeddour ◽  
Jamal Assaad ◽  
Emmanuel Moulin ◽  
Lucie Dupont ◽  
...  
Keyword(s):  
Lithium Niobate ◽  
Real Time ◽  
Experimental Tests ◽  
Fabrication Process ◽  
Two Dimensional ◽  
Low Frequencies ◽  
Impedance Analyzer ◽  
The Matrix ◽  
The One ◽  
Matrix Design

In this work, a two-dimensional (2D) Lithium Niobate (LiNbO3) 36°Y-cut micro-transducers (μTs) matrix design is presented. Two main steps define the fabrication process: electrode deposition and photolithography. These steps are preceded by the optical mask conception, which defines the 2D matrix pattern. In contrary to the one element case, this μTs matrix allows to automatically scan a desired structure in real time. The μTs matrix is characterized using an impedance analyzer. Furthermore, the experimental tests carried out in order to demonstrate the matrix functionality at low frequencies [200 - 800] kHz are presented.

Dielectric studies. Part XXIII. Relaxation data and apparent dipole moments of aniline and some disubstituted aromatic amines

1969 ◽  
Vol 47 (4) ◽  
pp. 681-686 ◽  
Author(s):  
S. W. Tucker ◽  
S. Walker
Keyword(s):  
Aromatic Amines ◽  
Dipole Moments ◽  
Frequency Dispersion ◽  
Dielectric Studies ◽  
Relaxation Data ◽  
Time Model ◽  
Electric Dipole Moments ◽  
Microwave Frequencies ◽  
Dielectric Absorption ◽  
Dielectric Results

Dielectric studies have been carried out at microwave frequencies on dilute solutions of aniline, p-chloro-, p-bromo-, and m-chloro-anilines, and o-, m-, and p-toluidines at 25 °C in cyclohexane and p-xylene. The static dielectric constant has also been measured at 2 MHz. In addition o- and m-toluidines have been measured at 50 °C and p-toluidine at 15, 35, and 50 °C.The dielectric results, particularly those at 70.01 GHz, establish that there is more than one relaxation process present and the data have been analyzed on a two relaxation time model, the longer of which τ1, is identified as molecular relaxation. The cause of the lower electric dipole moments found from this method as opposed to the non-dielectric absorption methods is discussed. It follows that there is either an additional higher frequency dispersion or (and) a high atomic polarization for aniline and o-, m-, and p-toluidines. Work at still higher frequencies is required to study this further and to establish more precise values of τ2.

Realization of Tunable Varactors Using Bi1.5Zn1.0Nb1.5O7 Thin Films

2009 ◽  
Vol 421-422 ◽  
pp. 153-156
Author(s):  
K. Sudheendran ◽  
K.C. James Raju
Keyword(s):  
Thin Films ◽  
Ground Plane ◽  
Silicon Substrates ◽  
Low Frequencies ◽  
Microwave Frequencies ◽  
Inner Radius ◽  
Voltage Dependent ◽  
Dc Bias ◽  
Fabrication And Characterization

Cubic pyrochlore bismuth zinc niobate thin films are known to exhibit voltage dependent dielectric properties. In this paper, we are demonstrating the fabrication and characterization of interdigital (IDC) and circular patch (CPC) capacitors using the pulsed laser deposited Bi1.5Zn1.0Nb1.5O7 (BZN) thin films on sapphire and platinised silicon substrates respectively. The IDCs fabricated are having 12 fingers of width 12 m each and separated by a gap of 8 m. The CPC are having circular patches with inner radius of 100 m and concentric ground plane with a radius of 300m. The electrical properties of these capacitors were characterized both at low frequencies and at microwave frequencies. The CPC varactors were having a tunability of 25% at 15 Volts. The calculated capacitance of the IDC varactor at 5.3 GHz with 0 V dc bias was 1.1 pF, which has got changed to 0.99 pF by the application of 30 Volts exhibiting a tunability of 10%.

A study of the negative ion FABMS of tris(perfluorophenyl)phosphine and related compounds: matrix effects

1995 ◽  
Vol 73 (8) ◽  
pp. 1321-1328
Author(s):  
Mandapati Saraswathi ◽  
Jack M. Miller ◽  
Tim R.B. Jones
Keyword(s):  
Mass Spectra ◽  
Fast Atom Bombardment ◽  
Matrix Effects ◽  
Negative Ion ◽  
The Matrix ◽  
Related Compounds

The mass spectra of tris(perfluorophenyl)phosphine obtained under negative ion Fast Atom Bombardment conditions showed formation of an unusual ion at m/z 397 attributed to ((C6F5)2PO2)−. The matrix effects involved in this reaction are discussed. Negative ion FAB spectra of tris(perfluorophenyl)arsine and tris(perfluorophenyl)stibine are also reported. Keywords: pentafluorophenylphosphine, -arsine, -stibine; negative ion FABMS; matrix effects.

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