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Oxidation kinetics for cis ‐9, trans ‐11 and trans ‐10, cis ‐12 isomers of CLA
Author(s) -
Minemoto Yasumasa,
Adachi Shuji,
Shimada Yuji,
Nagao Toshihiro,
Iwata Toshio,
YamauchiSato Yoshie,
Yamamoto Takaya,
Kometani Tadashi,
Matsuno Ryuichi
Publication year - 2003
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/s11746-003-0757-2
Subject(s) - autoxidation , autocatalysis , chemistry , kinetics , arrhenius equation , reaction rate constant , isomerization , cis–trans isomerism , activation energy , medicinal chemistry , polyunsaturated fatty acid , stereochemistry , photochemistry , catalysis , organic chemistry , fatty acid , physics , quantum mechanics
The autoxidation processes of the cis ‐9, trans ‐11 ( c 9, t 11) and trans ‐10, cis ‐12 ( t 10, c 12) isomers of CLA were separately observed at ca . 0% RH and different temperatures. The t 10, c 12 CLA oxidized faster than the c 9, t 11 isomer at all tested temperatures. The first half of the oxidation process of t 10, c 12 CLA obeyed an autocatalytic‐type rate expression, but the latter half followed first‐order kinetics. On the other hand, the entire oxidation process of c 9, t 11 CLA could be expressed by the autocatalytic‐type rate expression. The apparent activation energies and frequency factors for the autoxidation of the isomers were estimated from the rate constants obtained at various temperatures based on the Arrhenius equation. The apparent activation energies for the CLA isomers were greater than those for the nonconjugated n−6 and n−3 PUFA or their esters. However, the enthalpyentropy compensation held during the autoxidation of both the CLA and PUFA. This suggested that the autoxidation mechanisms for the CLA and PUFA were essentially the same.