On the phase transitions of cycloalkanes

Drotloff, Hansotto; Möller, Martin

doi:10.1016/0040-6031(87)88079-6

Cited by 22 publications

(3 citation statements)

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“…On the other hand, molecules that have significant increases in their conformational degrees of freedom on melting (or in their solid−solid phase transitions) will be expected to have increased values of Δ S tot because of the contribution of Δ S conf . An example is the cycloalkanes: those with 14 or fewer carbons in the ring have normal values of Δ S tot but for larger rings, where new conformers are expected on melting, Δ S tot is exceptionally large, and larger with larger rings . We now consider what is known about the structures and conformers of each of the thioethers examined here, especially to look for correlations between Δ S tot and conformational disorder.…”

Section: Discussionmentioning

confidence: 99%

“…An example is the cycloalkanes: those with 14 or fewer carbons in the ring have normal values of ∆S tot but for larger rings, where new conformers are expected on melting, ∆S tot is exceptionally large, and larger with larger rings. 37 We now consider what is known about the structures and conformers of each of the thioethers examined here, especially to look for correlations between ∆S tot and conformational disorder. We begin by mentioning that 1,4dithiane (6S2 in our designation) has a "normal" value of ∆S fus (56 J K -1 mol -1 ), 38 which indicates that it does not adopt more conformations in the liquid state than in the solid.…”

Section: Discussionmentioning

confidence: 99%

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Melting Behavior of Crown Thioethers: Correlation of Entropy Changes with Conformational Disorder

et al. 2002

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We have examined the following crown thioethers by differential scanning calorimetry from −90 °C, or lower, up to their melting points: 1,4,7-trithiacyclononane (9S3); 1,5,9-trithiacyclododecane (12S3); 1,4,7,10-tetrathiacyclododecane (12S4); 1,4,8,11-tetrathiacyclotetradecane (14S4); 1,4,7,10,13-pentathiacyclopentadecane (15S5); and 1,5,9,13-tetrathiacyclohexadecane (16S4). We have identified new solid−solid phase transitions above room temperature in 12S3, in the α-phase of 14S4, in 15S5, and in both the α-phase and β-phase of 16S4. Of those crown thioethers examined, only 9S3 and 12S4 do not show any solid−solid phase transitions. From an analysis of the entropy of fusion, we find that only the high-temperature solid phase of 16S4 is orientationally disordered. Analysis of the entropy changes associated with the solid−solid phase transitions and with fusion indicate that all except 12S4 have considerably more conformational freedom in the melt than in the room-temperature solid. Insight into these conformational changes is of considerable importance for understanding complexation of thioethers to metals.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Melting Behavior of Crown Thioethers: Correlation of Entropy Changes with Conformational Disorder

et al. 2002

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“…Melting point does not increase monotonically but rather reaches a plateau between 6 and 10 carbon atoms, before decreasing slightly, and then increasing to a melting point of 61 °C, for cyclododecane. Drotloff and Moller used DSC (Differential Scanning Calorimetry) to investigate the phase transition of large cycloalkane rings (Drotloff and Moller, 1987). They observed that melting point behavior is correlated to the amount of disorder in the liquid phase and that cycloalkanes with lower ring strain can adopt multiple, different conformations.…”

Section: Unsubstituted Cycloalkanesmentioning

confidence: 99%

Building Structure-Property Relationships of Cycloalkanes in Support of Their Use in Sustainable Aviation Fuels

et al. 2022

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In 2018 13.7 EJ of fuel were consumed by the global commercial aviation industry. Worldwide, demand will increase into the foreseeable future. Developing Sustainable Aviation Fuels (SAFs), with decreased CO2 and soot emissions, will be pivotal to the on-going mitigation efforts against global warming. Minimizing aromatics in aviation fuel is desirable because of the high propensity of aromatics to produce soot during combustion. Because aromatics cause o-rings to swell, they are important for maintaining engine seals, and must be present in at least 8 vol% under ASTM-D7566. Recently, cycloalkanes have been shown to exhibit some o-ring swelling behavior, possibly making them an attractive substitute to decrease the aromatic content of aviation fuel. Cycloalkanes must meet specifications for a number of other physical properties to be compatible with jet fuel, and these properties can vary greatly with the cycloalkane chemical structure, making their selection difficult. Building a database of structure-property relationships (SPR) for cycloalkanes greatly facilitates their furthered inclusion into aviation fuels. The work presented in this paper develops SPRs by building a data set that includes physical properties important to the aviation industry. The physical properties considered are energy density, specific energy, melting point, density, flashpoint, the Hansen solubility parameter, and the yield sooting index (YSI). Further, our data set includes cycloalkanes drawn from the following structural groups: fused cycloalkanes, n-alkylcycloalkanes, branched cycloalkanes, multiple substituted cycloalkanes, and cycloalkanes with different ring sizes. In addition, a select number of cycloalkanes are blended into Jet-A fuel (POSF-10325) at 10 and 30 wt%. Comparison of neat and blended physical properties are presented. One major finding is that ring expanded systems, those with more than six carbons, have excellent potential for inclusion in SAFs. Our data also indicate that polysubstituted cycloalkanes have higher YSI values.

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Physical Data of Oligomers

Rothe

1999

The Wiley Database of Polymer Properties

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On the phase transitions of cycloalkanes

Cited by 22 publications

References 5 publications

Melting Behavior of Crown Thioethers: Correlation of Entropy Changes with Conformational Disorder

Melting Behavior of Crown Thioethers: Correlation of Entropy Changes with Conformational Disorder

Building Structure-Property Relationships of Cycloalkanes in Support of Their Use in Sustainable Aviation Fuels

Physical Data of Oligomers

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