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Polymorphisme des triesters d'acides gras saturés et de tris(hydroxymethyl)-1,1,1 propane

Authors
Journal
Chemistry and Physics of Lipids
0009-3084
Publisher
Elsevier
Publication Date
Volume
7
Identifiers
DOI: 10.1016/0009-3084(71)90018-1

Abstract

Abstract By DTA, X-ray diffraction and IR spectrometry, it has been shown that triesters (RCOOCH 2) 3CC 2H 5 (RCOOC 12, C 14, C 16 and C 18) are monotropic, and can exist under four crystalline species: α, β′ I, β′ II and β, instead of α, β′ and β for the corresponding triglycerides. β′ I and β′ II have the same melting temperatures. β′ II differs from β′ I only by a small difference in the angle of tilt of hydrocarbon chains on their basic plane, and probably by a regular arrangement of ethyl groups. The arrangement of pitchfork-shaped molecules is head-to-tail in these structures, and long spacings correspond to two (α, β′ I and β′ II) of three (β and exceptionally β′ I for the dodecanoic derivative) chain lengths. Two νCO bands are encountered in the IR spectra of all forms. The C 16 derivative presents a transient sub β′ form. A supplementary study of the trioctadecanoate of tris(hydroxymethyl)-1,1,1 pentane has shown that the alkyl group substituted on the central carbon atom of the structure is responsible for the existence of the two β′ forms (of which melting temperatures are obviously distinct in this case). Moreover, this group seems to have a tendency to become parallel with other hydrocarbon chains when its length increases.

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