Spectroscopic study of internal rotation in chloroethanes

Allen, Geoffrey; Brier, P.N.; Lane, Geoffrey A.

doi:10.1039/tf9676300824

Cited by 46 publications

(10 citation statements)

References 7 publications

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“…Neither the 222-cm-1 band reported by Allen et al 23 nor the 239-cm-1 band reported by Daasch et al 22 were observed in the Raman spectrum of the liquid. Neither the 222-cm-1 band reported by Allen et al 23 nor the 239-cm-1 band reported by Daasch et al 22 were observed in the Raman spectrum of the liquid.…”

Section: B Chachcbmentioning

confidence: 75%

Low-Frequency Vibrations of Molecular Solids. X. CH3CCl3, CD3CCl3, CH3CCl2H, and CH3CF3

Durig

Craven

Lau

et al. 1971

The Journal of Chemical Physics

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The far-infrared spectra of solid CHaCCIa and CDaCCla have been investigated from 33 to 400 cm-l . Raman spectra of these solids have also been recorded. The internal torsional mode was observed at 290 and 206 cml in the infrared spectra of solid methylchloroform and methylchloroform-da, respectively. The threefold periodic barrier to rotation was calculated to be 5.5 kcal/mol. This barrier is compared to those previously reported by other techniques for this molecule and the reported value is much larger than that currently accepted. Four lattice vibrations, 46.9, 53.4, 57.7, and 67.5 cml were observed in the far-infrared spectrum of methylchloroform recorded at -190°C. Both the effect of temperature variation and deuterium substitution were investigated for these bands. These lattice modes shifted to lower frequency and became quite diffuse as the temperature approached the phase transition at -68°C. The low-frequency Raman spectrum of methylchloroform at -165°C showed one line at 38.6 cm-1 which shifted to 37.0 cml with deuteration. The infrared spectra of solid CHaCHCb and CHaCFa have been recorded between 140 and 400 cm-l . The internal torsional mode for 1, I-dichloroethane was observed at 232 and 231 cml for the solid and vapor, respectively. The threefold barrier to rotation was calculated to be 3.50 kcal/mol. The internal torsion for methylfluoroform was observed at 220 cm-l for the solid, and the barrier was calculated to be 3.29 kcal/mol. Substituent effects on the barrier heights are discussed.

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Section: B Chachcbmentioning

confidence: 75%

Low-Frequency Vibrations of Molecular Solids. X. CH3CCl3, CD3CCl3, CH3CCl2H, and CH3CF3

Durig

Craven

Lau

et al. 1971

The Journal of Chemical Physics

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“…In these simulations, we included harmonic atom-atom forces, three-body harmonic angle potentials, and a four-body dihedral Ryckaert-Bellemans potential allowing torsion of the molecule around the C-C bond. 27,28,29 A MDS was performed during 150000 ps for the largest system (6400 molecules). We used this run in order to calculate the Kirkwood correlation factor.…”

Section: Molecular Simulationsmentioning

confidence: 99%

Orientational relaxations in solid (1,1,2,2)tetrachloroethane

Tripathi

Mitsari

Romanini

et al. 2016

The Journal of Chemical Physics

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We employ dielectric spectroscopy and molecular dynamic simulations to investigate the dipolar dynamics in the orientationally disordered solid phase of (1,1,2,2)tetrachloroethane. Three distinct orientational dynamics are observed as separate dielectric loss features, all characterized by a simply activated temperature dependence. The slower process, associated to a glassy transition at 156±1 K, corresponds to a cooperative motion by which each molecule rotates by 180º around the molecular symmetry axis through an intermediate state in which the symmetry axis is oriented roughly orthogonally to the initial and final states. Of the other two dipolar relaxations, the intermediate one is the Johari-Goldstein precursor relaxation of the cooperative dynamics, while the fastest process corresponds to an orientational fluctuation of single molecules into a higher-energy orientation. The Kirkwood correlation factor of the cooperative relaxation is of the order of one tenth, indicating that the molecular dipoles maintain on average a strong antiparallel alignment during their collective motion. These findings show that the combination of dielectric spectroscopy and molecular simulations allows studying in great detail the orientational dynamics in molecular solids. 2 INTRODUCTIONWhile conventional (atomic) solids are made of atomic constituents with only translational degrees of freedom, so that their structure is totally determined by translation symmetry and fundamental excitations are vibrational in character, in molecular solids the constituent molecules possess also orientational (as well as internal) degrees of freedom, which lead to a richer variety of possible solid phases and to the existence of rotational excitations such as librations and orientational relaxations. A molecular solid can display complete translational and rotational order, as in a molecular crystal, or complete rototranslational disorder, as in a molecular glass. In between these two extremes, molecular solids also display phases (known as Orientationally disordered (OD) phases are generally formed by relatively small globular molecules such as derivatives of methane, 1,2,3 neopentane, 4 adamantane 5 or fullerene, 6 or by small linear ones such as ethane derivatives 7,8,9 and dinitriles. 10 OD solids exhibit many of the phenomenological features of glass formers, displaying in particular a cooperative rotational motion, called α relaxation, that undergoes a continuous, dramatic slow-down upon cooling, 11,12 leading in some cases to a glass-like 3 transition associated with rotational freezing. 13,14 Contrary to structural glasses, which do not exhibit any long-range order, OD phases are characterized by a translationally ordered structure and can therefore be more thoroughly characterized with the help of methods that exploit the translational symmetry such as Bragg diffraction, lattice models, or solid-state NMR spectroscopy. Even more importantly, since as mentioned OD phases are generally formed by molecular species with a simple structure ...

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“…Vibrational and NMR studies on the pure solvent have shown that the C 2 H 3 Cl 3 molecules exist in both conformations 59 in the liquid phase, with comparable concentrations, 61,62,63,64 and that each conformer has a specific vibrational signature. 60,65 Given that two conformers are present in the solution used to form the solvate, it is possible that they are also present in the solvate; however, the occurrence and relative concentration of conformers varies according to the nature of the system, 66 and depends on the subtle balance of intramolecular strains and the effects of the molecular environment. 45 For example, the gauche conformer is energetically more stable and by far the most abundant in the gas phase, 65,60 where intermolecular interactions are negligible.…”

Section: Dielectric Relaxations and Raman Spectroscopy Resultsmentioning

confidence: 99%

“…60,65 Given that two conformers are present in the solution used to form the solvate, it is possible that they are also present in the solvate; however, the occurrence and relative concentration of conformers varies according to the nature of the system, 66 and depends on the subtle balance of intramolecular strains and the effects of the molecular environment. 45 For example, the gauche conformer is energetically more stable and by far the most abundant in the gas phase, 65,60 where intermolecular interactions are negligible. In the disordered solid phase of pure C 2 H 3 Cl 3 only…”

Section: Dielectric Relaxations and Raman Spectroscopy Resultsmentioning

confidence: 99%

C₆₀ Solvate with (1,1,2)-Trichloroethane: Dynamic Statistical Disorder and Mixed Conformation

et al. 2016

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We present a full characterization of the orientationally disordered co-crystal of C 60 with (1,1,2)-trichloroethane (C 2 H 3 Cl 3 ) by means of x-ray diffraction, Raman spectroscopy and broadband dielectric spectroscopy. Our results include the determination of molecular conformations, lattice structure, positional disorder, and molecular reorientational dynamics down to the microsecond timescale. We find that, while in the disordered solid phase of pure C 2 H 3 Cl 3 the molecules exist only in the gauche conformation, both gauche and transoid conformers are present in the solvate, * Corresponding author. Tel: +34 934016568. E-mail: roberto.macovez@upc.edu. 2 where they occupy the largest interstitial cavities between the fullerenes species. The two C 2 H 3 Cl 3 conformers exhibit separate, independent relaxations, both characterized by simplyactivated behavior. The relaxation of the transoid conformer, which has twice the dipole moment of the gauche isomer, is significantly slower than that of the latter, due to the high polarizability of C 60 resulting in an electrostatic drag against the reorientations of the dipolar C 2 H 3 Cl 3 species.The observation of two distinct, simply-activated relaxations freezing at distinct temperatures indicates that they are not truly many-body relaxations, which may be rationalized considering that the C 2 H 3 Cl 3 molecules are separated by the relatively bulky C 60 spacers.3

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Spectroscopic study of internal rotation in chloroethanes

Cited by 46 publications

References 7 publications

Low-Frequency Vibrations of Molecular Solids. X. CH3CCl3, CD3CCl3, CH3CCl2H, and CH3CF3

Low-Frequency Vibrations of Molecular Solids. X. CH3CCl3, CD3CCl3, CH3CCl2H, and CH3CF3

Orientational relaxations in solid (1,1,2,2)tetrachloroethane

C₆₀ Solvate with (1,1,2)-Trichloroethane: Dynamic Statistical Disorder and Mixed Conformation

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Spectroscopic study of internal rotation in chloroethanes

Cited by 46 publications

References 7 publications

Low-Frequency Vibrations of Molecular Solids. X. CH3CCl3, CD3CCl3, CH3CCl2H, and CH3CF3

Low-Frequency Vibrations of Molecular Solids. X. CH3CCl3, CD3CCl3, CH3CCl2H, and CH3CF3

Orientational relaxations in solid (1,1,2,2)tetrachloroethane

C60 Solvate with (1,1,2)-Trichloroethane: Dynamic Statistical Disorder and Mixed Conformation

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C₆₀ Solvate with (1,1,2)-Trichloroethane: Dynamic Statistical Disorder and Mixed Conformation