Depolarized Rayleigh Scattering and Stereoregularity of Polystyrene Chains. II. Interpretation

Fourche, Georges; Lemaire, B.

doi:10.1295/polymj.4.476

Cited by 9 publications

(5 citation statements)

References 23 publications

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“…This is supported by conformational energy calculations (Gorin 1970) demonstrating that the most stable ring position is obtained when the C,-H bond is coplanar with the benzene ring. Furthermore, depolarized Rayleigh diffusion experiments (Fourche and Lemaire 1973) with the two isomers of 2,4-diphenylpentane have revealed that only limited torsion motions of the ring about this position are possible. Moreover, vibrational frequency 10b for the n-butyl-and n-amyl-benzenes is rather higher than that observed for ethyl-and n-propyl-benzene.…”

Section: Discussionmentioning

confidence: 99%

Far-infrared and Raman spectra of polystyrene model molecules

Jasse

Monnerie

1975

J. Phys. D: Appl. Phys.

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Infrared and Raman spectra have been recorded in the region below 420 cm-1 for the two simplest polystyrene model molecules. Attempts to assign the vibrational absorptions are presented. There are marked changes in the spectra with variations in the conformational structure of the alkyl chain. These changes are discussed in terms of coupling between the out-of-plane 10b mode of the benzene ring and deformation vibrations of trans conformation alkyl chain segments of different lengths.

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Section: Discussionmentioning

confidence: 99%

Far-infrared and Raman spectra of polystyrene model molecules

Jasse

Monnerie

1975

J. Phys. D: Appl. Phys.

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“…In particular we have used r;=l.48, ,*=1 and x=2O°; values determined from our previous experimental studies. 2 For heterotactic stereoisomer the theoretical molecular optical anisotropy has been calculated in the following ·** "f < 2> . manner.…”

Section: Molecular Optical Anisotropy and Conformational Analysismentioning

confidence: 99%

“…These results will be compared with those already published 4 • 8 elsewhere. The experimental and theoretical basis for the method used will not be developed here but may be found in ref [1][2][3][4][5][6].…”

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confidence: 99%

Conformational Analysis of Stereoisomers of Triphenylheptane by Depolarized Rayleigh Scattering

Fourche¹,

Jasse

Maelstaf

1977

Polym J

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S:Average molecular optical anisotropies 3 of TPH in cyclohexane solution at 25°C was determined* by measuring the scattered depolarized intensity from the solutions at a wavelengh of 5460 A. The technique used has been previously described. 3 ' 1 The accuracy of is * In practice the intensity measurements are carried out by comparison with a standard liquid, cyclohexane, for which these has been determined at a wavelength of 5460 A a scattered depolarized intensity per unit volume and unit of incident photometric illumination of 23, 15-10-8 cm-1• 537

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“…These compounds can be considered polystyrene dimers and trimers, respectively. Far-infrared and depolarized Rayleigh scattering methods have been applied in the study of phenyl ring motion in these compounds, while conformational populations have been investigated by NMR vicinal coupling measurements, − depolarized Rayleigh scattering (optical anisotropy), , far-infrared and Raman spectroscopy, ultrasonic relaxation measurements, , and epimerization reactions. , These compounds have also been the subject of both molecular mechanics − and limited ab initio electronic structure calculations . These studies seem to establish racemic tt (r- tt ) as the lowest energy conformer of DPP.…”

Section: Introductionmentioning

confidence: 99%

Conformations of 2,4-Diphenylpentane: A Quantum Chemistry and Gas-Phase Molecular Dynamics Simulation Study

Smith¹,

Ayyagari²,

Jaffe

et al. 1998

J. Phys. Chem. A

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We report on the relative conformer energies and rotational energy barriers for meso and racemic 2,4-diphenylpentane (DPP) from ab initio electronic structure calculations. It is found that dispersion interactions between phenyl rings strongly influence the conformational geometries, necessitating the inclusion of electron correlation in both geometry optimizations and energy calculations. Furthermore, basis set superposition contributions to the phenyl-phenyl interactions, estimated by extracting the phenyl rings from the optimized DPP geometries and computing the basis set superposition error for the resulting benzene dimer configurations, are significant. An atomistic molecular mechanics force field is parametrized to reproduce our best values for the conformational energies and rotational energy barriers in DPP obtained from ab initio calculations. Conformational energy contour maps are presented for the DPP enantiomers, and their salient features are discussed. Gas-phase molecular dynamics simulations of DPP have been performed using the quantum chemistry based force field. Important entropic contributions to the conformer populations, due primarily to restricted phenyl group rotation, are discussed.

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Depolarized Rayleigh Scattering and Stereoregularity of Polystyrene Chains. II. Interpretation

Cited by 9 publications

References 23 publications

Far-infrared and Raman spectra of polystyrene model molecules

Far-infrared and Raman spectra of polystyrene model molecules

Conformational Analysis of Stereoisomers of Triphenylheptane by Depolarized Rayleigh Scattering

Conformations of 2,4-Diphenylpentane: A Quantum Chemistry and Gas-Phase Molecular Dynamics Simulation Study

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