X-Ray Investigation of Crystalline Cyclopentane and Neohexane<sup>1</sup>

Post, B.; Schwartz, Robert S.; Fankuchen, I.

doi:10.1021/ja01155a028

Cited by 47 publications

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“…The focus of this work is on the breathing mode of the cycle around 890 cm –1 (bottom panel of Figure ), whereas the peaks around 2900 cm –1 are characteristic of CH 2 stretching modes. It is important to note that solid CP can exist in three phases depending upon the temperature: a crystalline phase (phase I, T < 118 K) and two plastic phases (phase II, 118 < T < 136 K; phase III, 138 < T < 178 K). − The bottom panel of Figure shows that each CP phase exhibits distinctive Raman signatures. Crystalline phase ( T = 77.2 K) and plastic phase ( T = 122.3 and 141.9 K for phases II and III, respectively) signatures are easily disentangled; three sharper peaks (881.3, 896, and 904.1 cm –1 ) characterize the crystalline phase, whereas two broader peaks are seen in each of the plastic phases.…”

Section: Resultsmentioning

confidence: 99%

Phase Behavior of Clathrate Hydrates in the Ternary H₂O–NH₃–Cyclopentane System

Pétuya

Choukroun

et al. 2020

ACS Earth Space Chem.

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Titan, Saturn's largest satellite, is the only icy moon with a dense atmosphere that is composed mainly of N 2 . Methane, the second most abundant constituent, would be depleted in only 30−100 million years by active photochemistry, suggesting replenishment from Titan's interior. Under Titan's near-surface conditions, clathrate hydrates are the stable form of methane and ice together, making them a likely methane reservoir. Cassini−Huygens observations suggest that ammonia is the main source of Titan's atmospheric N 2 . Ammonia is known to decrease the melting point of water ice and some clathrate hydrates, such as those of tetrahydrofuran. The present study investigates the interaction of ammonia with cyclopentane clathrate hydrates (atmospheric analogue for methane clathrates) via a detailed examination of phase behavior using micro-Raman spectroscopy, differential scanning calorimetry, and X-ray diffraction. The results show that ammonia has the same effect on the stability of the cyclopentane clathrate as on tetrahydrofuran clathrate and ice by lowering the dissociation temperature by several tens of degrees and inducing incongruent melting. Ammonia does not interact directly with cyclopentane and does not appear to be incorporated into the cyclopentane clathrate structure, whether in the lattice or within the cages. A similar effect could be expected for methane clathrates. The presence of ammonia in Titan's crust would thus destabilize methane clathrates, resulting in outgassing and replenishment of atmospheric methane.

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Section: Resultsmentioning

confidence: 99%

Phase Behavior of Clathrate Hydrates in the Ternary H₂O–NH₃–Cyclopentane System

Pétuya

Choukroun

et al. 2020

ACS Earth Space Chem.

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“…13 Powder patterns of all the phases obtained were taken with a standard Debye-Schemer powder camera using techniques which have been described elsewhere.I4 Nickel-filtered CuKa radiation was used throughout the investigation. …”

Section: X-ray Diffraction Apparatusmentioning

confidence: 99%

Polymorphism of the Crystalline Methylchloromethane Compounds

Rudman

Post²

1968

Molecular Crystals

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Polymorphism of the methylchloromethane compounds, (CH3),CC14-,, where n varies from 0 to 4, has been studied using lowtemperature X-ray diffraction techniques. Single crystals of both high and low-temperature phases were grown and crystal data were obtained for the various phases. The crystal structure of the phase of t-butyl chloride which is stable between -54 and -90" was determined. On the basis of the present investigation, the conclusion is reached that the hightemperature modifications are dynamically disordered, in agreement with the results of n.m.r. and dielectric studies.

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“…Dunning 1961). Only one example so far reported is known to the authors: cyclopentane, which has h.c.p, structure (Post, Schwartz & Fankuchen, 1951).…”

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Crystal lattices of the plastic crystals norbornadiene, norbornylene and norbornane

Jackson¹,

Strange²

1972

Acta Crystallogr Sect B

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The crystal lattices of the plastic crystals norbornadiene, norbornylene and norbornane have been determined using an X-ray powder technique. Norbornadiene and norbornylene each exhibit only one plastic phase, characterized by a hexagonal close-packed structure. The results obtained show that for norbornadiene a = 5.89, c = 9.51/~, and for norbornylene a = 6"08, c = 9.81/~,. Norbornane has two distinct plastic phases. The one at lower temperature has a hexagonal close-packed structure, a=6-17, c= 10.03 A, while above the phase transition at 306 °K an f.c.c, structure, a= 8"73 A, is observed.

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X-Ray Investigation of Crystalline Cyclopentane and Neohexane¹

Cited by 47 publications

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Phase Behavior of Clathrate Hydrates in the Ternary H₂O–NH₃–Cyclopentane System

Phase Behavior of Clathrate Hydrates in the Ternary H₂O–NH₃–Cyclopentane System

Polymorphism of the Crystalline Methylchloromethane Compounds

Crystal lattices of the plastic crystals norbornadiene, norbornylene and norbornane

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X-Ray Investigation of Crystalline Cyclopentane and Neohexane1

Cited by 47 publications

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Phase Behavior of Clathrate Hydrates in the Ternary H2O–NH3–Cyclopentane System

Phase Behavior of Clathrate Hydrates in the Ternary H2O–NH3–Cyclopentane System

Polymorphism of the Crystalline Methylchloromethane Compounds

Crystal lattices of the plastic crystals norbornadiene, norbornylene and norbornane

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X-Ray Investigation of Crystalline Cyclopentane and Neohexane¹

Phase Behavior of Clathrate Hydrates in the Ternary H₂O–NH₃–Cyclopentane System

Phase Behavior of Clathrate Hydrates in the Ternary H₂O–NH₃–Cyclopentane System