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.

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.

Microwave Absorption and Relaxation Behavior of Some Simple Ketones in Dilute Solutions

1975 ◽  
Vol 53 (1) ◽  
pp. 23-28 ◽  
Author(s):  
M. P. Madan
Keyword(s):  
Relaxation Time ◽  
Thermodynamic Parameters ◽  
Microwave Absorption ◽  
Reasonable Agreement ◽  
Relaxation Times ◽  
Relaxation Behavior ◽  
The Other ◽  
Dielectric Absorption ◽  
Dielectric Data ◽  
Thermodynamic Processes

The dielectric absorption of solutions of 2-hexanone, 4- and 5-nonanone, and 2-decanone has been examined in the microwave region over a range of temperatures in n-heptane, cyclohexane, and benzene. The relaxation times and the thermodynamic parameters for the activated states have been determined using the measured dielectric data. The values of relaxation time are in reasonable agreement at the temperature at which there are available known data. Both the relaxation behavior and the thermodynamic processes are discussed and, where possible, compared with corresponding results of the other workers.

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.

Dielectric Studies. Part XXXV. Relaxation Studies of Benzaldehyde and Fourpara-Substituted Aideliydes

1974 ◽  
Vol 52 (18) ◽  
pp. 3229-3234 ◽  
Author(s):  
P. F. Mountain ◽  
S. Walker
Keyword(s):  
Hydrogen Bonding ◽  
Relaxation Time ◽  
Intermolecular Hydrogen Bonding ◽  
Dielectric Studies ◽  
Molecular Relaxation ◽  
Relaxation Data ◽  
Dielectric Absorption ◽  
The Mean ◽  
Relaxation Studies ◽  
Xylene Solution

The dielectric absorption has been determined for benzaldehyde, p-fluoro-, p-chloro-, p-bromo-, and p-nitro-benzaldehyde in p-xylene solution at mainly five or six frequencies in the 6.70 to 70.1 GHz region. For all three p-halo-substituents the mean relaxation time values indicate that some mechanism faster than molecular relaxation occurs whereas none was apparent in benzaldehyde itself. A detailed study has been made of p-chlorobenzaldehyde in p-xylene solution at five temperatures, and the data have been analyzed into contributions from a molecular relaxation process and a shorter relaxation time τ2. In the p-xylene solutions of benzaldehyde the relaxation data indicate weak intermolecular hydrogen bonding between the solute and the solvent which is probably of the type [Formula: see text]

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.

Dielectric Behaviour in the MHz range of cis-bis (glycynato)Cu(II) monohydrate and (glycylglycinato)Cu(II) trihydrate in Water

1976 ◽  
Vol 31 (9) ◽  
pp. 1085-1088 ◽  
Author(s):  
P. U. Sakellaridis ◽  
E. K. Karageorgopoulos
Keyword(s):  
Activation Energy ◽  
Aqueous Solution ◽  
Dipole Moment ◽  
Relaxation Time ◽  
Dielectric Properties ◽  
Charge Separation ◽  
Rotational Relaxation ◽  
Kcal Mole ◽  
Dielectric Absorption ◽  
Molecular Radius

Abstract The dielectric properties of Cu(gly)2 and Cu(glygly) in diluted aqueous solution were examined in the MHz range at 273 to 313 K. The complexes exhibit dielectric absorption in the ranges 5.09X107 to 9.34X107 Hz and 4.63X107 to 8.01X107 Hz, respectively, depending on concentration and temperature. This absorption was attributed to rotational relaxation of the unhydrated and monohydrated complexes. The following data for the two complexes in solution at 293 K have been obtained, respectively: dipole moment 19.3 D and 34.0 D, charge separation 2.01 A and 3.54 Å, relaxation time 2.3X10-9 sec and 2.6X10-9 sec, molecular radius 6.36 Å and 6.47 Å, activation energy for the relaxation process 5.6 kcal mole-1 for both complexes.

Dielectric Studies. Part XXXIV. Relaxation Evidence for Complex Formation of 1,4-Dioxan with Chelated Ring Systems

1972 ◽  
Vol 50 (17) ◽  
pp. 2799-2805 ◽  
Author(s):  
M. D. Magee ◽  
S. Walker
Keyword(s):  
Relaxation Time ◽  
Carbon Tetrachloride ◽  
Complex Formation ◽  
Loss Factor ◽  
Significant Interaction ◽  
Specific Interaction ◽  
Ring System ◽  
Dielectric Studies ◽  
Time Data ◽  
Microwave Frequencies

The dielectric constant (ε′) and loss factor (ε″) of solutions of (i) 8-hydroxyquinoline in cyclohexane, carbon tetrachloride, p-xylene and 1,4-dioxan, (ii) o-nitrophenol in n-heptane, cyclohexane, carbon tetrachloride, and 1,4-dioxan, (iii) 2,4-dinitrophenol in 1,4-dioxan, and (iv) 2,6-dinitrophenol also in 1,4-dioxan have been recorded at four microwave frequencies and at 25 °C. A comparison of the relaxation time data of 1-nitro-naphthalene with that of 8-hydroxyquinoline in a number of solvents indicates that a strong specific interaction occurs between the latter solute and the solvent 1,4-dioxan which leads to the formation of a complex. In addition, a comparative study of nitrobenzene and o-nitrophenol indicates a similar phenomenon. Strong interaction of the 1,4-dioxan with an atom or atoms in the chelated ring system appears to take place which produces a larger reorienting species than the solute molecule itself and appreciably lengthens the relaxation time, although the data do not establish the point of attachment of the 1,4-dioxan to the chelated ring. The complex formation is accompanied by an additional component to the dipole moment. For the dinitrophenols significant interaction with the solvent p-xylene complicates the interpretation of the relaxation time data, although in the 2,4-dinitrophenol the formation of a complex is indicated in 1,4-dioxan.

Dielectric relaxation of some aliphatic ester molecules in solutions

1979 ◽  
Vol 57 (7) ◽  
pp. 1035-1038 ◽  
Author(s):  
M. P. Madan
Keyword(s):  
Relaxation Time ◽  
Dielectric Relaxation ◽  
Relaxation Times ◽  
Activation Parameters ◽  
Dielectric Absorption ◽  
Aliphatic Ketones ◽  
Dielectric Data ◽  
Aliphatic Ester ◽  
Aliphatic Esters ◽  
Intramolecular Rotation

The dielectric absorption of several aliphatic esters has been examined in the microwave region over a range of temperatures in n-heptane, cyclohexane, and benzene. The relaxation times and the thermodynamic parameters have been determined using the measured dielectric data. The values of the relaxation time for those solutions for which there are available known data agree well with other determinations. The relaxation times and the various molar activation parameters have been discussed in terms of dipole reorientation by molecular and intramolecular rotation. It would appear that the relaxation behavior of aliphatic esters is similar to that for other aliphatic molecules, such as aliphatic ketones studied previously.

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.

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