Thermal analysis of long-chain ketones and the extrapolated equilibrium melting for polyethylene

Nakasone, Keiko; Urabe, Yoshiko; Takamizawa, Kanichiro

doi:10.1016/0040-6031(96)02929-2

Cited by 9 publications

(13 citation statements)

References 19 publications

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“…Linear n -alkanes with carbon numbers less than 80 are known to take the extended chain conformation as the energetically most favored form in the crystalline state, and the smooth flat interface is always formed between lamellae. − Introduction of small functional groups such as the carbonyl or hydroxyl group to the middle of those linear chains hardly disturbs the crystalline structure of their linear homologues. − The subcell structure is the same for all samples examined, and their melting temperatures become higher than those of the linear homologues because of dipole−dipole interaction or hydrogen bonding, whereas the solid−solid phase transitions characteristic of pure linear alkanes disappear due to this interaction. ,− …”

Section: Introductionmentioning

confidence: 99%

Crystal Structures of n-Alkanes with Branches of Different Size in the Middle

et al. 2005

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We synthesized four branched n-alkane samples C35-C1, C35-C4, C35-C6, and C35-C4Ph with the same number of carbons as the main chain, n = 35, to which the methyl, butyl, hexyl, and butyl phenyl groups were respectively attached at the middle, and also the corresponding linear homologue of C35, and studied their crystalline structures from DSC, IR, and Raman spectroscopy, X-ray diffraction measurement, and computer simulation. Solid-solid phase transitions characteristic of linear alkane C35 are not observed for any branched alkanes, and their melting temperatures Tm are lowered to 325.2, 318.5, 314.3, and 314.1K, respectively. Main chains of branched alkane molecules are not folded, irrespective of length and chemical structure of branches, but are extended to take the planar zigzag form in the solid state. The branches of C35-C4 and C35-C6 are also aligned inside the crystal in the extended form. Data analyses on solution-grown crystallized samples reveal that, with increasing the branch length, their crystal structures transform from polymorphic forms of the orthorhombic (P2(1)2(1)2(1)) and the triclinic (P) for C35-C1 and C35-C4 to the unique triclinic form for C35-C6 and C35-C4Ph, so as to minimize extra surface energy invoked by introduction of long branches.

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Section: Introductionmentioning

confidence: 99%

Crystal Structures of n-Alkanes with Branches of Different Size in the Middle

et al. 2005

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“…There is an arbitrary scaling factor for the parameters in the previous paragraph, but the literature provides Δ H f values for nine symmetrical long‐chain ketones from C23 to C43 . Including these in the least‐squares fitting for scaling purposes, together with another 8 symmetrical ketones, requires reducing Δ S f as described above.…”

Section: Introductionmentioning

confidence: 99%

Understanding Long‐Chain Melting Points, Fritz Breusch, and Interface Thermodynamics

McBride

Bertman

2017

Israel Journal of Chemistry

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Ah omologouslyi somorphous series of compounds can allow determinationo fl ocal contributions to crystal properties. Historically,m elting points have contributed little to structuralt heory,b ut those of as eries of longchain diacylp eroxides allow the measurement of localized structural contributions to solid-state thermodynamics, and demonstrate that ab romines ubstituent at al amellar interface can make negative contributions to both the enthalpy and entropy of fusion, thus acting more "liquid-like" when in the crystal than when in the melt. We discuss how Istanbul, and opposition to Hitler, led FriedrichB reusch and his studentst om easure at least 1242 accurate melting points, and how this legacy may prove valuable in understanding crystalline solids, especially those that show odd-even melting-point alternation.Keywords: Friedrich Breusch · history of science · interfaces · isomorphism · odd-even melting-point alternation[a] J.

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“…Center-Branched Alkanes. Introduction of small functional groups such as carbonyl or hydroxyl group at the middle point of the linear chains, H 3 C(CH 2 ) n –CO–(CH 2 ) n CH 3 or H 3 C(CH 2 ) n –CHOH–(CH 2 ) n CH 3 , modifies the regular packing structure of the original linear n -alkane homologues. − The subcell structure of the methylene parts is essentially the same as that of linear homologues. The melting temperature becomes higher than that of the corresponding linear n -alkane because of the existence of strong dipole–dipole interactions between the neighboring CO bonds or relatively strong intermolecular hydrogen bonds between the OH groups.…”

Section: Introductionmentioning

confidence: 99%

“…The melting temperature becomes higher than that of the corresponding linear n -alkane because of the existence of strong dipole–dipole interactions between the neighboring CO bonds or relatively strong intermolecular hydrogen bonds between the OH groups. The solid-state phase transitions detected for linear alkanes are not observed for the center-substituted alkane derivatives due to these additional interactions. − …”

Section: Introductionmentioning

confidence: 99%

Systematic Study of Aggregation Structure and Thermal Behavior of a Series of Unique H-Shape Alkane Molecules

et al. 2011

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The H-shape alkanes of various arm lengths have been synthesized successfully through the Grignard reaction. The detailed investigation of these novel compounds may allow us to widen the topological chemistry field furthermore. The molecular form and molecular packing structure in the crystal lattice have been revealed successfully on the basis of X-ray structure analysis as well as the analysis of Raman longitudinal acoustic modes (LAM) sensitive to the alkyl zigzag chain segments. The molecular conformation in the crystal lattice is deformed markedly from the originally imagined H-shape. In the cases of C3HOH to C6HOH, for example, the molecules are packed in a complicated manner and the OH···O hydrogen bonds govern the whole intermolecular interactions mainly. Since the alkyl segmental length is not very long, the conformational change is not very drastic, i.e., the small configurational entropy. Synergic effect of the hydrogen bonds and the small configurational entropy gives the higher melting point as known from the thermal data. On the other hand, in the cases of C10HOH and C12HOH, one of the long alkyl chain arms is found to be bent by 90° so that all of the alky chain segments of planar-zigzag conformation can be packed as closely as possible, and the intermolecular OH···O hydrogen bonds are also formed effectively without any mistake. As a result, the contribution of nonbonded intra- and intermolecular van der Waals interactions between the trans-zigzag alkyl chain segments become major, and the coupling of this enthalpy effect with the larger configurational entropy effect of the molecular shape results in the decrement of the melting point which approaches gradually that of longer n-alkane compound. In this way a sensitive balance between the nonbonded van der Waals interactions, the OH···O hydrogen bonds, as well as the configurational entropy effect gives the characteristic thermal behavior of the H-shape compounds. The thus-newly synthesized H-shape alkane compounds should give us new insight into the packing topology of complicated molecules, leading to the development of new functionality unexpected for normal linear alkane compounds.

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Thermal analysis of long-chain ketones and the extrapolated equilibrium melting for polyethylene

Cited by 9 publications

References 19 publications

Crystal Structures of n-Alkanes with Branches of Different Size in the Middle

Crystal Structures of n-Alkanes with Branches of Different Size in the Middle

Understanding Long‐Chain Melting Points, Fritz Breusch, and Interface Thermodynamics

Systematic Study of Aggregation Structure and Thermal Behavior of a Series of Unique H-Shape Alkane Molecules

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