NMR in the solid isomers twistane and adamantane

Graham, John D.; Choi, Jong K.

doi:10.1063/1.430737

Cited by 9 publications

(3 citation statements)

References 24 publications

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“…Experimental investigations of adamantane exist for both the crystalline and plastic crystalline phases. Calorimetric, infrared, differential thermal analysis (DTA), and NMR studies have been reported. − Studies by Chang and Westrum show that the molar enthalpies (molar entropies) of transition for adamantane for the crystal to the plastic crystal phase and the plastic crystal to the liquid phase are 3.38 kJ/mol (16.2 J/(mol K)) and 13.8 kJ/mol (25.4 J/(mol K)), respectively. Kabo et al have looked at the relationship of the thermodynamic data to the orientational disorder as a function of temperature.…”

Section: Introductionmentioning

confidence: 99%

Pressure-Induced Ordering in Adamantane: A Monte Carlo Simulation Study

Murugan

Yashonath

2005

J. Phys. Chem. B

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Isothermal-isobaric ensemble Monte Carlo simulation of adamantane has been carried out with a variable shape simulation cell. The low-temperature crystalline phase and the room-temperature plastic crystalline phases have been studied employing the modified Williams potential. We show that at room temperature, the plastic crystalline phase transforms to the crystalline phase on increase in pressure. Further, we show that this is the same phase as the low-temperature ordered tetragonal phase of adamantane. The high-pressure ordered phase appears to be characterized by a slightly larger shift of the first peak toward a lower value of r in C-C, C-H, and H-H radial distribution functions as compared to the low-temperature tetragonal phase. The coexistence curve between the crystalline and plastic crystalline phase has been obtained approximately up to a pressure of 4 GPa.

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Section: Introductionmentioning

confidence: 99%

Pressure-Induced Ordering in Adamantane: A Monte Carlo Simulation Study

Murugan

Yashonath

2005

J. Phys. Chem. B

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“…Therefore, we tried to estimate the molecular motion by comparing the activation energies for typical molecular motions that have been observed in conventional organic compounds and polymers. For example, the activation energy for the general reorientation of a plastic crystal of adamantane has been found to be 10.5 kJ mol −1 [10]. As another example, the activation energy for flip-flop motion in the benzene rings in bisphenol-A polycarbonate has been found to be 26 kJ mol −1 [11].…”

Section: Resultsmentioning

confidence: 96%

Field-swept 33S NMR study of elemental sulfur

Yamada

Kitagawa

Takahashi³

2015

Chemical Physics Letters

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“…In some cases, the low-temperature phase may still exhibit some degree of static orientational disorder as a remnant of the dynamic disorder that existed in the high-temperature phase. Examples of organic materials that undergo such order–disorder phase transitions include rotator phase solids, in which highly symmetrical molecules [for example, hexamethylbenzene, − adamantane, − and tetrakis(trimethylsilyl)silane − ] undergo facile reorientational motions within their crystal structures in the high-temperature phase and transform to structures of lower symmetry in the low-temperature phase. Solid inclusion compounds (for example, urea − and thiourea − inclusion compounds) also exhibit order–disorder phase transitions in which dynamic disorder in the high-temperature phase concerns the reorientational motions of guest molecules inside a solid host structure, and the phase transition to the ordered phase is associated with “freezing” of the motion of the guest molecules and lowering of the symmetry of the host structure.…”

Section: Introductionmentioning

confidence: 99%

Temperature-Dependent Structural Properties, Phase Transition Behavior, and Dynamic Properties of a Benzene Derivative in the Solid State

Zhou

Patterson

Williams

et al. 2019

Crystal Growth & Design

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We report the solid-state structural properties and phase transition behaviour of 1,4-dibromo-2,3,5,6tetramethylbenzene, demonstrating that this material undergoes an order-disorder phase transition below ambient temperature (at ca. 154 K on cooling and ca. 160 K on heating). In both the hightemperature and low-temperature phases, the crystal structure is based on π-stacking of the molecules. In the crystal structure of the high-temperature phase, the bromine occupancy in each substituent site is ca. 1/3 and the methyl group occupancy in each substituent site is ca. 2/3, consistent with statistical orientational disorder of the molecule between six distinct orientations. Natural-abundance solid-state 2 H NMR spectroscopy confirms that, at ambient temperature, this disorder is dynamic via rapid molecular reorientation about an axis perpendicular to the aromatic ring. In the low-temperature phase, the bromine and methyl substituents occupy preferred sites within the crystal structure, with the distribution of site occupancies becoming progressively more ordered on decreasing temperature.

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NMR in the solid isomers twistane and adamantane

Cited by 9 publications

References 24 publications

Pressure-Induced Ordering in Adamantane: A Monte Carlo Simulation Study

Pressure-Induced Ordering in Adamantane: A Monte Carlo Simulation Study

Field-swept 33S NMR study of elemental sulfur

Temperature-Dependent Structural Properties, Phase Transition Behavior, and Dynamic Properties of a Benzene Derivative in the Solid State

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