Polymorphism of linoleic acid (cis-9, cis-12-octadecadienoic acid) and alpha-linolenic acid (cis-9, cis-12, cis-15-octadecatrienoic acid).
Crystallization and polymorphic properties of linoleic acid (cis-9, cis-12-Octadecadienoic acid) (LA) and alpha-linolenic acid (cis-9, cis-12, cis-15-Octadecatrienoic acid) (alpha-LNA) have been studied by optical microscopy, differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The DSC analyses presented three polymorphs in LA, and two polymorphs in alpha-LNA. The XRD patterns of the higher- and lower-temperature forms in LA and alpha-LNA showed orthorhombic O'(//)+O-like and O'(//) subcell, which were similar to those of alpha- and gamma-forms of mono-unsaturated fatty acids, respectively. From the solvent crystallization of LA and alpha-LNA in acetonitrile, single crystals of the higher temperature polymorphs have been obtained. The crystal habits of truncated rhombic shape were also similar to those of alpha-forms of the mono-unsaturated fatty acids. The enthalpy and entropy values of fusion and dissolution of the alpha-forms of LA, alpha-LNA and oleic acid showed that the two values decreased with increasing number of the cis-double bond.
Ueno
S
S
Faculty of Applied Biological Science, Hiroshima University, 1-4-4 Kagamiyama, 739-8528, Higashi-Hiroshima, Japan. sueno@hiroshima-u.ac.jp
Miyazaki
A
A
Yano
J
J
Furukawa
Y
Y
Suzuki
M
M
Sato
K
K
D002152:Calorimetry, Differential Scanning; D007536:Isomerism; D019787:Linoleic Acid / Q000737:chemistry*; D013816:Thermodynamics; D014961:X-Ray Diffraction; D017962:alpha-Linolenic Acid / Q000737:chemistry*
D017962:alpha-Linolenic Acid; D019787:Linoleic Acid