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ON THE ANTIOXIDANT EFFECTIVENESS OF N,N´–SUBSTITUTED P-PHENYLENEDIAMINES

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Author(s): Zuzana Cibulková | Erik Klein | Vladimír Lukeš

Journal: Petroleum and Coal
ISSN 1337-7027

Volume: 46;
Issue: 2;
Start page: 42;
Date: 2004;
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Keywords: Quantum chemical calculations | PM3 | antioxidants | antioxidant effectiveness | p-phenylene diamines

ABSTRACT
The ground-state geometry of six N,N’-substituted p-phenylenediamines (PPDs): N-phenyl-N’-dimethyl-butyl-p-phenylenediamine (6PPD), N-phenyl-N’-isopropyl-p-phenylenediamine (IPPD), N-phenyl-N’-(α-methylbenzyl)-p-phenylenediamine (SPPD), N-(2-methoxybenzyl)-N’-phenyl-p-phenylenediamine (MBPPD), N-benzyl-N’-phenyl-p-phenylenediamine (MBPPDH), N-(1-methyl-1-phenylethyl)-N’-phenyl-p-phenylene-diamine (CPPD) molecules, their radical structures and the energy characterisation of these molecules and radicals were theoretically investigated using PM3 method. Our calculations reveal the most probable radical formation in the order SPPD > MBPPD > MBPPDH > 6PPD > IPPD > CPPD. The theoretical values have been compared with the values obtained by the analysis of structural units contributions based on the results of non-isothermal DSC measurements. The results show that the most likely process is homolytic cleavage of C–H bond at the carbon atom in the neighbourhood of the amino nitrogen atom and the sterical arrangement is related to the antioxidant effectiveness of the antioxidants under study. The suggested models can be used for the interpretation and prediction of experimental data what is important from the technological point of view.
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