Dynamical dimer structure and liquid structure of fatty acids in their binary liquid mixture: decanoic/octadecanoic acid and decanoic/dodecanoic acid systems.
Dimer structure and liquid structure of fatty acids in their binary mixtures such as decanoic acid (DA)/octadecanoic acid (SA) and DA/dodecanoic acid (LA) were studied through the measurements of self-diffusion coefficient (D), differential scanning calorimetry (DSC), density and viscosity. The obtained phase diagrams showed that DA and SA form a eutectic in the solid state but partly a solid solution in the SA-rich region; DA and LA form an incongruent-melting compound which forms a eutectic with DA. In the liquid mixture of DA and SA, the D of DA is larger than that of SA over the entire range of compositions and tends to approach the D of SA with increasing SA-mole fraction; the D of DA in the DA/LA system is also larger than that of LA especially in the LA-poor region and steeply approaches that of LA with increasing LA-mole fraction. These D values and phase diagrams were compared with those for the binary mixtures of n-alkanes (C14/C20, C19/C20 and C20/C24); it is concluded that the two kinds of fatty acids always form their individual homodimers in their liquid mixtures regardless of their compositions and temperatures.
Iwahashi
Makio
M
School of Science, Kitasato University, 1-15-1 Kitasato, Sagamihara 228-8555, Japan. maki@kitasato-u.ac.jp
Takebayashi
Shintaro
S
Taguchi
Masakazu
M
Kasahara
Yasutoshi
Y
Minami
Hideyuki
H
Matsuzawa
Hideyo
H
D000473:Alkanes / Q000737:chemistry; D002152:Calorimetry, Differential Scanning; D003652:Decanoic Acids / Q000737:chemistry*; D003720:Densitometry; D004058:Diffusion; D019281:Dimerization; D005227:Fatty Acids / Q000737:chemistry*; D007850:Lauric Acids / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D044367:Phase Transition; D012996:Solutions / Q000737:chemistry; D013229:Stearic Acids / Q000737:chemistry*; D014783:Viscosity
D000473:Alkanes; D003652:Decanoic Acids; D005227:Fatty Acids; D007850:Lauric Acids; D012996:Solutions; D013229:Stearic Acids; C030358:lauric acid; C031183:stearic acid; C031071:decanoic acid