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Mechanisms of antioxidant action: Transformations involved in the antioxidant function of metal dialkyl dithiocarbamates. III
Author(s) -
AlMalaika S.,
Marogi A.,
Scott G.
Publication year - 1987
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1987.070330502
Subject(s) - antioxidant , metal , action (physics) , function (biology) , chemistry , organic chemistry , stereochemistry , biology , physics , microbiology and biotechnology , quantum mechanics
The behaviors of iron, nickel, and zinc dialkyl dithiocarbamates were compared with the corresponding thiuram disulphide in their reaction with cumene hydroperoxide (CHP) at 110°C. The metal complexes exhibit both homolytic and heterolytic processes and transformation products formed during the above reactions and not the initial metal complexes were found to be responsible for the heterolytic decomposition process. However, the nature of the initial transformation products in the case of the iron and nickel complexes differed from those of the corresponding zinc complex. In the former case the corresponding disulfide was shown to be the initial transformation product while there was no evidence for the formation of disulfide in the case of the zinc complex. This difference appears to be responsible for the observed different kinetic behavior of CHP decomposition in the presence of the nickel and iron complexes from that in the presence of zinc. This thiuram disulfide behaves quite differently from the metal complexes in that heterolytic decomposition of hydroperoxide predominates at all molar ratios of the disulphide to the CHP. The hydroperoxide decomposition curves in this case show only one step in contrast to the metal complexes which show a multistep behavior, and this was shown to correspond to the third catalytic stage in the reaction of the metal complexes. Comparison of the rate constant of this step with that of the final step of the metal complexes shows a close resemblance to the case of the iron and nickel and is quite different from that of the zinc complex, confirming the intermediacy of the disulfide in the former cases but not in the latter.