Kinetic study of the reaction between tocopheroxyl radical and unsaturated fatty acid esters in benzene |
| |
Authors: | Kazuo Mukai Yuji Okauchi |
| |
Affiliation: | (1) Department of Chemistry, Faculty of Science, Ehime University, 790 Matsuyama, Japan |
| |
Abstract: | A kinetic study of the reaction between a tocopheroxyl radical and unsaturated fatty acid esters has been undertaken. The
rates of allylic hydrogen abstraction from various unsaturated fatty acid esters (ethyl oleate2, ethyl linoleate3, ethyl linolenate4, and ethyl arachidonate5) by the tocopheroxyl radical (5,7-diisopropyltocopheroxyl6) in benzene have been determined spectrophotometrically. The second-order rate constants, k3, obtained are 1.04×10−5 M−1s−1 for2, 1.82×10−2 M−1s−1 for3, 3.84×10−2 M−1s−1 for4, and 4.83×10−2 M−1s−1 for5 at 25.0°C. Thus, the rate constants, kabstr/H, given on an available hydrogen basis are k3/4=2.60×10−6 M−1s−1 for2, k3/2=9.10×10−3 M−1s−1 for3, k3/4=9.60×10−3 M−1s−1 for4, and k3/6=8.05×10−3 M−1s−1 for5. The kabstr/H values obtained for the polyunsaturated fatty acid esters3,4, and5 containing H-atoms activated by two π-electron systems are similar to each other, and are about three orders of magnitude
higher than that for the ethyl oleate2 containing H-atoms activated by a single π-system. From these results, it is suggested that the prooxidant effect of α-tocopherol
in edible oils and fats may be induced by the above hydrogen abstraction reaction. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|