Antioxidants and stabilizers. IL. 1,3,5‐trimethyl‐2,4,6‐tris (1‐tert‐butylperoxy‐3,5‐ditert‐butylcyclohexa‐2,5‐diene‐4‐onylmethyl)benzene: Formation, properties and effect on the oxidation of tetralin and isotactic polypropylene

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.

Antioxidants and stabilizers. L. Transformation of the 1,3,5‐tris(4‐hydroxy‐3,5‐di‐tert‐butylbenzyl)cyanuric acid into alkylperoxycyclohexadienones, their properties and effects on the oxidation of tetralin and polypropylene

Lerchová

Pospı́šil

1974

Antioxidants and stabilizers. LII. Sensitized photooxidation of 2,6‐di‐tert‐butyl‐4‐methylphenol

Taimr¹,

Pospı́šil²

1974

In connection with a complex investigation of the transformations of stabilizers during the ageing of polymers, the photooxidation of 2,6‐di‐tert‐butyl‐4‐methylphenol (IV) sensitized with methylene blue in methanol was investigated. If the reaction takes place in a dilute solution, phenol(IV) is oxidized with singlet oxygen forming 2,6‐di‐tert‐butyl‐4‐methyl‐4‐hydroperoxy‐2,5‐cyclohexadiene‐1‐one (V). In a concentrated solution phenol (IV) is attacked by an excited sensitizer which gives rise to a corresponding aryloxy radical; transformations of the latter yield 2,6‐di‐tert‐butyl‐4‐methoxymethylphenol (VI). The further reaction of phenol (IV) is slower, but similar to phenol (IV): by a reaction with singlet oxygen 2,6‐di‐tert‐butyl‐4‐methoxymethyl‐4‐hydroperoxy‐2,5‐cyclohexadienel‐one (VIII) is formed, while a reaction with the excited sensitizer again gives rise to the corresponding aryloxyl. Transformations of the latter produce 3,5‐di‐tert‐butyl‐4‐hydroxybenzaldehyde (X). Under oxidizing conditions the compounds (VIII) and (X) undergo further transformation to yield 2,6‐di‐tert‐butyl‐1,4‐benzoquinone (IX).

Antioxidants and stabilizers LXVII.. Transformation of 4,4′‐thiobis(2‐methyl‐6‐tert‐butylphenol) under conditions of inhibited autoxidation

Jiráčková

Pospı́šil

1978

The mechanism of the antioxidative effect of thiobisphenols in the inhibition of autoxidation of polyolefins initiated by the decomposition of hydroperoxides was studied by means of a model reaction of 4,4-thiobis(2-methyI-6-tert-butylphenol) (I) with tertbutylhydroperoxide in the presence Co(I1)acetyl acetonate. Products isolated from the reaction mixture prove that in the inhibition of autoxidation, thiobisphenols break as phenols the propagation chains of radical autoxidation, while they decompose as sulphides the hydroperoxides into nonradical products. ZUSAMMENFASSUNG:Der Mechanismus der antioxidativen Wirkung von Thiobisphenolen wahrend der Inhibierung der durch Hydroperoxidzersetzung initiierten Autoxidation von Polyolefinen wurde durch eine Modellreaktion von 4,4-Thiobis(2-methyl-6-tert-butylphenol) (I) mit tert-Butylhydroperoxid in Anwesenheit von Kobalt(I1)-acetylacetonat untersucht. Die aus der Reaktionsmischung isolierten Produkte bestatigen, daD Thiobisphenole als Phenole die Wachstumsreaktion in der inhibierten Autoxidation unterbrechen und als Sulfide die Hydroperoxide zu nichtradikalischen Produkten zersetzen.