The decomposition of 2,6‐di‐tert‐butyl‐4‐methyl‐4tert‐butylperoxy‐2,5‐cyclohexadienone (I) in n‐heptane solution irradiated with light having wavelengths of 333 nm and 436 nm and in the solid phase irradiated with solar light was investigated. The composition of the reaction mixture was studied by UV and IR spectrometry and chromatographically (gel permeation, thin layer). The radical species was recorded using the electron pulse resonance (EPR) method.

The effect of halogenated and alkylated dihydric phenols on the autoxidation process of tetralin and cumene initiated at 65°C with AIBN has been investigated. The character of substitution effects the antioxidative activity of the derivatives of the pyrocatechol and hydroquinone series in a different way. All halogenated pyrocatechols were less active than unsubstituted pyrocatechol. Their antioxidative activity increased in both substrates proportionally to the number of the halogen atoms. On the other hand the introduction of chlorine atoms into the hydroquinone ring led to a considerable increase in the antioxidative activity compared to hydroquinone and to its alkyl derivatives. In both substrates isomeric dihydric phenols exhibited different retardation of the oxidation course in the step following the induction period. The reasons for the different behavior are discussed.

The transformation of 1,3.5-tris(4-hydroxy-3,S-dI-tert-butylbenzyl~yanuric acid (I), designed as an antioxidant for polyolefins, during its reaction with tert-butylperoxyls was studied. In tert-butyl alcohol two oxidation products, I 1 and 111, are formed, while in benzene the reaction proceeds faster with formation of cyclohexadienone 111. The structures of the oxidation products were confirmed, their thermal properties were measured (by DTA) and the effect on the oxidation of tetralin and isotactic polypropylene was determined. The oxidative transformation makes trisphenol I lose its antioxidative property. The different behaviour of trisphenol I and another important phenolic antioxidant. namely, 1,3,5-trimethyl-2,4,6-tris(4-hydr~xy-3,5-di-t~rt-butylben~yl)benzenc (IV) under the conditions of inhibited oxidation of polyolefins is discussed. ZUSAMM ENFASSUNC;:Die Emwandlung von 1,3,5-Tris(4-hydroxy-3.5-di-tert-butylbcn~yl~yanursaure (I). die als Antioxidans fur Polyolcfine dient, wurdc wahrcnd der Rcaktion mit tert-Butylpcroxyl untersucht. Zwci Oxidationsproduktc I1 und I l l entstehen in tert-Butylalkohol; die Umwandlung liuft schnellcr in Bcnzol, und als Produkt cntstcht hier nur das Cyclohcxadienon 111. F.s wurdc die Struktur der Oxidationsprodukte bestatigt, die thermischen Eigenschaften mittels DTA gemcsscn und dcr Einflul3 auf den Oxidationsverlauf von Tetralin und Polypropylcn verfolgt. WBhrend dcr oxidativcn Umwandlung verlicrt das Trisphenol I seine antioxidativen Eigenschaften. Der I!nterschied in der AktivitBt von Trisphenol I und von cinem anderen wichtigcn phcnolischen Antioxidans, 1,3.5-Trimethyl-2.4,6-tris(4hydroxy-3.5-di-tcrt-butylbcnzy1)benzol (IV), unter den Bedingungcn der inhibicrtcn Oxydation von Polyolefinen wird diskutiert.

The transformation of the antioxidant 1,3,5-trimethyl-2,4,6-tris(3,5-ditert-butyl-4-hyd-roxybenzy1)benzene (I) by the oxidation with tert-butyl hydroperoxide in the presence of Co(I1)acetylacetonate was investigated. The reaction in tert-butyl alcohol gives rise to product 11 of partial oxidation, while in benzene cyclohexadienone 111 is formed.The oxidation products were defined, and their thermal properties and behaviour in light were determined. The oxidative transformation of trisphenol I leads to a loss of its antioxidative activity. The oxidation products I 1 and 111 at the temperature of their formation d o not exhibit an unfavourable effect on the process of thermal oxidation. However, after heating of the hydrocarbon substrate containing them to a temperature close to their decomposition point they act as initiators. They undergo photochemical transformation already at room temperature and give colour to the polymer. ZUSAMM ENFASSUNG :Es wurdc die Umwandlung des Antioxidans 1,3,5-Trimethyl-2,4,6-tris(3,5-ditert-butyl-4hydroxybenzyl)benzol (I) wahrend der Reaktion mit tert-Butylhydroperoxid in Anwescnheit von Kobalt(I1)-acetylacetonat verfolgt. In tert-butylalkoholischer Losung entsteht das Produkt I1 durch partielle Oxidation, in Benzol dagegen ist das Cyclohexadienon 111 das Hauptprodukt. Die Strukturen der beiden Oxidationsprodukte I1 und 111 wurden bestimmt und ihre thermischen und photochemischen Eigenschaften untersucht. Die antioxidative Aktivitat des Trisphenols I geht durch seine stufenweise oxidative Umwandlung verloren. Die Oxidationsprodukte I1 und 111 haben bei der Temperatur ihres Entstehens keinen negativen EinflulJ auf den Verlauf der thermischen Oxidation. Nach Erwhnen des organischen Substrats in die Nahe ihrer Zcrsetzungstemperatur wirken sie dagegen initiierend. Sie unterliegen schon bei Zimmertemperatur einer photochemischen Umwandlung und verfarben das Polymere.

Selected alkylated and halogenated derivatives of pyrocatechol and hydroquinone were oxidized with oxygen at 150°C in trichlorobenzene. The results allow an evaluation of participation of the direct oxidation of the antioxidant in the overall mechanism of its deactivation during the stabilization of polyolefins. Further data were obtained by oxidation performed in an alkaline medium. Specific relationships between the direct oxidation of halogenated dihydric phenols and their antioxidative activity in polypropylene and low‐molecular weight hydrocarbons are discussed.