Kinetics of Methyl Oleate Oxidation in Microemulsion Stabilized
with Triton Х-100. I. Lipid-Soluble Initiator
2,2'-Azo-bis-isobutyronitrile1
O. V. Semikashevaа, R. A. Nasibullinaа, L. R. Yakupovaа, *, and R. L. Safiullinа
а Ufa Institute of Chemistry, Ufa Federal Research Center, Russian Academy of Sciences, Ufa, Bashkortostan, 450054 Russia
Correspondence to: *е-mail: stargar@inbox.ru
1Abbreviations and notation: AIBN, 2,2'-azo-bis-isobutyronitrile; τ, induction period; F, degree of inhibitor effect; wi, initiation rate; w, oxidation rate; f, stoichiometric inhibition coefficient; ki, initiation rate constant; k1 and k2, chain propagation rate constants; kp, initiator decomposition rate constant; k6, chain termination rate constant of oxidation by recombination of peroxyl radicals; k7, inhibition rate constant; k2/(2k6)–0.5, oxidizability parameter; InH, inhibitor, RH, oxidized substrate (methyl oleate, MO); R•, ROOH, alkyl and peroxyl radicals and hydroperoxide formed from the substrate; CTAB, cetyl trimethylammonium bromide; SDS, sodium dodecyl sulfate.
Received 21 April, 2021
Abstract—The kinetics of oxidation of methyl oleate in a microemulsion stabilized by Triton Х-100 has been studied. To generate peroxyl radicals, a lipid-soluble initiator 2,2'-azo-bis-isobutyronitrile was used. The oxidation of methyl oleate in the microemulsion was found to occur by the radical chain mechanism with quadratic-law chain termination. The optimum concentrations of surfactant and methyl oleate were determined. The initiation rate was measured and the oxidizability parameter of methyl oleate in the microemulsion was determined by the inhibitor method. The rate constants of the reaction of the peroxyl radical of methyl oleate with α-tocopherol and trolox (fk7, L mol–1 s–1, 333 K) were measured: (2.9 ± 0.2) × 104 and (4.0 ± 0.2) × 104 , respectively.
Keywords: radical chain oxidation, methyl oleate, sodium dodecyl sulfate, Triton Х-100, 2,2'-azo-bis-isobutyronitrile, inhibition, α-tocopherol, trolox
DOI: 10.1134/S0023158421050098