Synthesis and crystal spacings of certain long-chain paraffins, ketones and secondary alcohols

Piper, Stephen Harvey; Chibnall, Albert Charles; Pollard, A.; Smith, James; Williams, Edward F.

doi:10.1042/bj0252072

Cited by 136 publications

(38 citation statements)

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“…In diffraction patterns from paraffins, the existence of interlamellar disorder is most prominently expressed by the low angle 00l reflections (Piper, et al, 1931;Fischer, 1971) where, by convention, the c-axis is the longest in the unit cell. If the paraffin is heated near the melting point, there is a buildup of non-planar conformations near the chain ends, well-characterized by spectroscopic measurements (Maroncelli, et al, 1985a;Kim, et al, 1989a).…”

Section: Introductionmentioning

confidence: 99%

Electron crystallography of the polymethylene chain. 4. Defect distribution in lamellar interfaces of paraffin solid solutions

Dorset¹

2000

Zeitschrift Für Kristallographie - Crystalline Materials

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As is also found for paraffin lamellar crystals heated near the rotator or melt transition, the major change in electron diffraction patterns imposed by lamellar disorder in binary or multicomponent solid solutions is the attenuation and intensity modification of low-angle (00l) reflections. Using a Gaussian model for atomic occupancies near the interface, a systematic basis is found for the interfacial disorder thickness, describing the phenomenological void' distribution at the lamellar interface. (Vibrational spectroscopy has shown that this is actually a distribution of non-planar chain conformations.) Single crystal electron diffraction data from various co-soluble paraffin chain assemblies, used previously to determine their crystal structures (but also including a new determination for n-C 36 H 74 / n-C 38 H 78 /n-C 40 H 82 1:1:1), are re-analyzed so that further distinctions can be made among simple binary and ternary solid solutions, multicomponent waxes, and low molecular weight polyethylene. Expressions of the latter polyethylene structure, involving`bridging molecules' can be found in certain natural insect and plant waxes.

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Section: Introductionmentioning

confidence: 99%

Electron crystallography of the polymethylene chain. 4. Defect distribution in lamellar interfaces of paraffin solid solutions

Dorset¹

2000

Zeitschrift Für Kristallographie - Crystalline Materials

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“…Part of this effect can be attributed to a broademng of the diffraction intensity curves and a r esulting apparent shif t of the maxima to smaller angles. Piper [28] found that inhomogeneous mixtures of paraffins frequently give long spacings which are indistinguishable from those of pure compounds and that long spacings alone are a poor means oJ identifying paraffins. However, with reasonably pure samples of known chain length, small-angle spacings offer a convenient way to identify phase, and a spacing greater than expected from fi gure 3 would indicate uneven-chain-end planes and hence probably impurities.…”

Section: X-ray Long Spacingsmentioning

confidence: 99%

“…Impurity effects have been the major cau se ?f confusion in t be study of n-paraffins, In cbfll n compounds, tbe usual impurities are other cbai l~ compounds of similar length since, othOl: types, 01 impurities are easily removed, Vanous bmary mIXtures of paraffins have been studied [27][28][29][30] in order to determine the effects of pa,raffin impurities on paraffins and it is not unrea onab1e to suppose that the observed effects would apply qualitatively to other long chain impuritie such as olefins. Rather complex binary phase diagrams have been CODstructed [29,53] to explain binary behavior but several general conclusions can be made.…”

Section: 5 Impurity Effectsmentioning

confidence: 99%

An analysis of the solid phase behavior of the normal paraffins

Broadhurst¹

1962

J. RES. NATL. BUR. STAN. SECT. A.

625

381

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A set of best values for t he te mperatures a nd enthalpies of fusion alld transition for the n-paraffins is presented. From a n a nalysis of these data a general qualitative t heory of the phase behavior of the n-paraffins is developed. Four di stinct. crystal structures-h exagonal, t riclinic, monoclinic, and orthorhombic-describe t he solid phases of all n-paraffins with more than nine carbon atoms in the cha in. The la tter t wo structures beco me equivalent at longer chain lengt hs. Odd-even d ifferences are resolved in terms of reasonable diffet'ences in end group packing, a nd t he smooth in crease in melting a nd transition t emperature " 'ith increasing chain length is attributed to a dec rease in t he r atio of end groups to ch ain gro ups. Double t ransitions a re predicted for several pure n-paraffins a bove n-C34H 70 • Impurity effec ts are isolated from the pure n-para ffin properties a nd disc ussed. The equat ion, TM (O K ) = 414.3 (n-1. 5) ! (n + 5.0) is presented as a correct d escript ion of the m elting te mperatures (T M ) of all n-paraffins above n-C44H IlO • Suffi cient data t o p ermit an acc urate extrapolation of the enthalpie and entropies of fu sion to the infinite-c bain limit are not avail a ble.

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“…1 The distribution of chain disorder has often been studied in lamellar waxes. It readily became apparent that, in terms of diffraction experiments, a suitable model at layer surfaces for dissimilar chain lengths within a lamella would include a distribution of fractional methylene atomic occupancies, 5 with the greatest deviation from unity occurring at the surface. Spectroscopic measurements, on the other hand, indicate that the packing arrangement might be more complicated than just partial methylene group occupancies.…”

Section: Introductionmentioning

confidence: 99%

Crystal Structure of Wax Lamellar InterfacesA Residual Petroleum Fraction Characterized by Electron Crystallography

Rademeyer¹,

Dorset

2001

J. Phys. Chem. B

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After a multicomponent paraffin assembly was constructed to model a petroleum residue wax (M w /M n ) 1.009), its structure was characterized by electron crystallography. Consistent with a single lamellar spacing, two endotherms in a DSC scan are typical of paraffin chain solid solutions and represent the premelt transition to a "rotator" phase and the true melt. The average chain packing in the crystal structure is that of the paraffin n-C 32 H 66 , in space group Pca2 1 with a ) 7.42, b ) 4.96, and c ) 85.0 Å. An attempt to account for the lamellar disorder with a chain-end occupancy model based on the chemical distribution of chain lengths is only partially successful. A better fit is found when lower chain-end occupancies are used. This discrepancy could be due to conformational defects in which the chain end atoms do not lie on strict methylene subcell lattice sites.

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Synthesis and crystal spacings of certain long-chain paraffins, ketones and secondary alcohols

Cited by 136 publications

References 0 publications

Electron crystallography of the polymethylene chain. 4. Defect distribution in lamellar interfaces of paraffin solid solutions

Electron crystallography of the polymethylene chain. 4. Defect distribution in lamellar interfaces of paraffin solid solutions

An analysis of the solid phase behavior of the normal paraffins

Crystal Structure of Wax Lamellar InterfacesA Residual Petroleum Fraction Characterized by Electron Crystallography

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