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Effect of carbonyls on the reactivity of polyenes in autoxidation
Author(s) -
Krasnokutskaya I. S.,
Leontieva S. V.,
Finkelshtein E. I.,
Khodonov A. A.,
Shvets V. I.
Publication year - 2003
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.600
Subject(s) - autoxidation , polyene , chemistry , reactivity (psychology) , radical , photochemistry , retinyl acetate , molecule , conjugated system , organic chemistry , computational chemistry , polymer , retinol , vitamin , medicine , biochemistry , alternative medicine , pathology
Autoxidation of the biologically active polyenes β‐carotene, canthaxanthin, retinyl acetate, methyl retinoate, retinal and 3,7,11,11‐tetramethyl‐10,15‐dioxo‐2,4,6,8‐hexadecatetraenal (diketoretinal) in solid amorphous films was investigated. The course of the process was followed by electronic and IR spectroscopy. The overall activation energies were obtained. It was shown that insertion in the polyene molecule of a carbonyl group conjugated with polyene chain results in a drastic decrease in the reactivity towards molecular oxygen. The results are discussed and explained on the basis of radical stabilization energy, E S (R · ), as a driving force of the autoxidation process. Semi‐empirical AM1 calculations of Δ H f of some retinyl polyenes and polyenyl radicals were carried out and the C—H bond strengths and E S (R · ) values of corresponding polyenyl radicals were evaluated. It was shown that the incorporation of a carbonyl group in the polyene results in a decrease in the overall autoxidation rate due to the decrease in both the initiation and propagation rates. Copyright © 2003 John Wiley & Sons, Ltd.