A variety of oxidation products of antioxidants based on N,N′-substituted p-phenylenediamines

Antioxidant effectiveness of dehydrogenated p-phenylene diamines through NMR calculations

“…In our previous study (Puškárová, 2015) we have investigated experimentally and evaluated by B3LYP calculations the NMR shifts of several PPD antioxidants in DMSO. We have found that their AEM increases with NMR shifts of both amine hydrogens, of the nitrogen between aromatic rings and probably of the tertiary carbon atom neighboring to the nitrogen between aromatic ring and the side aliphatic chain in agreement with the above mentioned theory of Simon et al (Cibulková, 2005a;Cibulková, 2005b;Polovková, 2006;Gatial, 2007;Cibulková, 2009;Rapta, 2009;Cibulková, 2010;. On the other hand, the NMR shifts of the amine nitrogens between aromatic ring and the side aliphatic chain exhibit a reverse trend.…”

“…The benzoquinonediimine-type products may finally undergo hydrolytic or condensation reactions by forming benzoquinonemonoimine-type structures or N-heterocyclic compounds (Cataldo, 2001;Cataldo, 2002). Simon et al investigated the relation between the structure of the PPD antioxidants and their efficiency in polyisoprene rubber (PIR) by non-isothermal DSC (Differential Scanning Calori metry) measurements (Cibulková, 2005a;Cibulková, 2005b;Polovková, 2006;Gatial, 2007;Cibulková, 2009;Rapta, 2009;Cibulková, 2010;. As the concentration of free radicals during the induction period determines the rate of the oxidation reaction, which can be reduced using antioxidants, the antioxidant activity can be evaluated as the ratio of the lengths of the induction periods t i of the stabilized (PIR + AOx) and unstabilized (PIR) polymer since the stability or non-stability of the polymer is brought about the same structural units both in stabilized and unstabilized polymer.…”

“…Simon et al (Cibulková, 2005a;Cibulková, 2005b;Polovková, 2006;Gatial, 2007;Cibulková, 2009;Rapta, 2009;Cibulková, 2010; have found that the effectiveness of a series of antioxidants under study is indirectly proportional to the dissociation energy of the C-H bond at the tertiary carbon atom in the neighbourhood of the nitrogen atom. Substitution of all hydrogen atoms at this carbon atom leads to a loss of antioxidant properties.…”

“…In order to find the relation between the structures of PPD antioxidants and their AEM values some of them were investigated theoretically by Density Functional Theory (DFT) model studies as well (Polovková, 2006;Gatial, 2007;Rapta, 2009;Kortišová, 2005;Breza, 2008;Rimarčík, 2010). Real PPD structures in the protected materials significantly depend on solid state effects and so it is very problematic to find suitable characteristics of the PPD molecules which not much depend on their conformations.…”

Electrochemical, microscopic and spectroscopic characterization of benzene diamine functionalized single walled carbon nanotube-cobalt (II) tetracarboxy-phthalocyanine conjugates

“…For CoTCPc, CoTCPc/BDA-SWCNT (mix) and CoTCPc-BDA-SWCNT, these peaks are due to the first ring oxidation of the phthalocyanine (Co(III)Pc À1 /Co(III)Pc À2 ). The peak observed on the BDA-SWCNT is due to the oxidation of the phenyl-amine group that is attached on the SWCNT wall [36,37]. The CV of phenyl-amine alone showed a peak at around 0.7 V. Fig.…”