Comparison of energy barrier data from dielectric, n. m. r. and ultrasonic techniques

Tay, S. P.; Walker, S.; Wyn‐Jones, E.

doi:10.1016/0378-4487(78)80018-1

Cited by 26 publications

(9 citation statements)

References 14 publications

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“…( I ) For a single dielectric process the absorption curves are very broad and symmetrical and fit the Fuoss-Kirkwood curve well within the limits of experimental error (10,11,15). When asymmetrical absorption curves are obtained, this may suggest overlap of absorption (1 l,22).…”

Section: Discussionmentioning

confidence: 96%

“…Dielectric measurements on solutes dispersed in a polystyrene matrix and the evaluation of the results have been described previously (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25). The polystyrene matrix was prepared in the way described by Davies and Swain (10).…”

Section: Experimental and Resultsmentioning

confidence: 99%

“…In p-toluidine C, = 0.25 which is a condition for a good Budo analysis for z,. In the present work it has been anticipated that the rate of molecular relaxation would be more retarded in the medium of a polystyrene matrix than the intramolecular relaxation processes which could well be detected separately from the molecular one, and consequently accurate barriers could possibly be determined (10,11).…”

Section: Introductionmentioning

confidence: 99%

“…disk containing the solute (10,11,14). When the concentration of the solute in the polystyrene matrix is low (< 5 to 7 mol%), the AH, value for the molecular process is independent of concentration (27).…”

Section: Fig 2 Eyring Rate Plot For 4-aminobiphenyl In Polystyrenementioning

confidence: 99%

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Dielectric absorption of a few aromatic amines in a polystyrene matrix

Tay¹,

Walker²

1981

Can. J. Chem.

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Dielectric absorption studies in the ranges 77–373 K and 102–107 Hz have been made on aniline, poly(4-aminostyrene), p-toluidine, 4-chloroaniline, 1-aminopyrene, and 4-aminobiphenyl in a polystyrene matrix. An intramolecular process has been observed in poly(4-aminostyrene) and 1-aminopyrene with enthalpies of activation of 25 and 26 kJ mol−1 respectively. The enthalpy of activation of the intramolecular process is of the same order as that found for the torsional barrier in aniline and 4-fluoroaniline. The most likely candidate for the intramolecular process appears to be rotation of the amino group about the carbon–nitrogen bond.

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Section: Discussionmentioning

confidence: 96%

Section: Experimental and Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Fig 2 Eyring Rate Plot For 4-aminobiphenyl In Polystyrenementioning

confidence: 99%

See 2 more Smart Citations

Dielectric absorption of a few aromatic amines in a polystyrene matrix

Tay¹,

Walker²

1981

Can. J. Chem.

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“…Dielectric constants and the loss factor of solutes in the polymer matrix were obtained in the frequency range 50 to lo5 Hz using a General Radio 1615A capacitance bridge incorporated with a suitable measuring cell from liquid nitrogen temperature to approximately 350 K. A detailed description of the apparatus, measurement techniques, and accuracy of the measurements is reported elsewhere (14,15 For personal use only.…”

Section: Methodsmentioning

confidence: 99%

Dielectric relaxation processes of some dialkyl disulfides

Khwaja¹,

Walker²

1983

Can. J. Chem.

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. J. Chem. 61, 2107 (1983).Dielectric relaxation studies have been performed for dimethyl, diethyl, di-isopropyl, di-n-butyl, di-tert-butyl, and di-n-octyl disulfides in a polystyrene matrix. For the last five compounds the absorption appears in two temperature regions. The relaxation data for the higher temperature regions are consistent with intramolecular rotation around the S-S bond with accompanying flexibility in the alkyl chains. The enthalpy barrier to this relaxation process is -29 kJ mol-' and is the trclr~s (lower) barrier. This value is typical for all six dialkyl disulfides. The most likely interpretation of the low temperature process is that there is segmental relaxation of the alkyl chains which also involves movement of the main dipoles (S-S and S-C).On a effect& des Ctudes de relaxation dielectrique sur les disulfures de mkthyle, d'kthyle, d'isopropyle, de n-butyle, dc tert-butyle et de n-octyle dans un support de polystyrene. Pour les 5 derniers composes I'absorption se manifeste dans deux zones de temperature. Les donnees de relaxation pour la region de haute temperature sont en accord avec une rotation intramoleculaire autour de la liaison S-S avec une flexibilitC dans la chaine alkylCe. La barriere d'enthalpie de ce processus de relaxation est de 29 kJ mol-' environ et c'est la barriere trans (la plus basse). Cette valeur est typique pour tous les six disulfures d'alkyle. L'interpretation la plus courante de processus a basse tempkrature prkconise une relaxation segmentaire des chaines d'alkyies qui implique Cgalement Ie mouvement des dipoles principaux (S-S et S-C).[Traduit par le journal] IntroductionThe existence of a barrier to rotation around the S-S link of a disulfide was established at least two decades ago, but experimentally determined barrier heights span quite a range. The rotation was frequently treated on a two-fold energy barrier model although in many measured values the cis and trans barriers were not separately identified. Two of the earlier studies on infrared spectra of dialkyl disulfides were those of Thompson and Trotter (1) and of Sheppard (2). At about the same time Scott and co-workers (3) reported the vibrational assignments of dimethyl disulfide (3a), diethyl disulfide (3b), and dimethyl di-n-propyl disulfide (3c), together with the collection of early data of infrared and Raman frequencies for thermodynamic studies. Detailed infrared and Raman spectra of di-tert-butyl disulfide were measured later by Scott and co-workers (3d). These investigations showed the presence of some rotational freedom about the S-S link. Through the use of calculated and observed entropy and heat capacity, an effective barrier height of 28.4 kJ mol-I (3c) for the internal rotation around the S-S bond of dimethyl disulfide was deduced. El-Sabban and Scott (3e), using infrared data, reported a sim-

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Ultraschalluntersuchungen in flüssigen und plastischen Phasen

Kreutzenbeck

Ledwig

Würflinger

1983

Ber Bunsenges Phys Chem

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Different devices have been developed for ultrasonic measurements at atmospheric and elevated pressures up to 1 kbar. The velocities of sound for liquid toluene, 2,3‐dimethylbutane, cyclohexane, and camphene have been determined. In the case of 2,3‐dimethylbutane also preliminary absorption measurements at elevated pressures have been performed, according to which the activation volume for the hindered internal rotation is negligible. Furthermore some plastic phases have been studied. The velocities of sound (longitudinal mode) of cyclohexane and camphene increase considerably on freezing in contradiction to the findings of others. Additional measurements of the transverse modes allow a rough estimation of the elastic stiffness constants.

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Comparison of energy barrier data from dielectric, n. m. r. and ultrasonic techniques

Cited by 26 publications

References 14 publications

Dielectric absorption of a few aromatic amines in a polystyrene matrix

Dielectric absorption of a few aromatic amines in a polystyrene matrix

Dielectric relaxation processes of some dialkyl disulfides

Ultraschalluntersuchungen in flüssigen und plastischen Phasen

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