Phenols phenyl-substituted

Phenyl-substituted phenols constitute a novel class of chain-breaking antioxidants (4). Their action with and without / -activated thioethers has been investigated in polypropylene (PP) (5,6,7). 

The synthetic scheme adopted for the preparation of the chainbreaking phenolic antioxidants involves the oxidation of a phenyl-substituted phenol (I) to the corresponding p-benzoquinone (II) followed by reduction to the hydroquinone (III). The hydroquinone is allowed to react then with cyanuric chloride and its derivatives or with alcohols as shown in Scheme 1. 

Antioxidant Activity of Some Phenyl-Substituted Phenols (VII) in PP at 180°C (Oxygen-Uptake Test). In Table I the results obtained with some phenyl-substituted phenols are shown and compared with some well-known ferf-butyl-substituted phenols. A general conclusion from this table is the marked synergism between phenyl-substituted phenols and -activated thioethers compared with the ferf-butyl-substituted analog. Since the measurements are done in a closed tube, the influence of the volatility of the thiodipropionates is not reflected in the induction periods. An explanation for the anomalous behavior of phenyl-substituted phenols in synergistic mixtures can be found in the results of the model reactions, carried out with phenoxyl radicals and sulfides or sulfoxides (see "Model Reactions ). 

Antioxidant Activity of Triazine-Based, Phenyl-Substituted Phenols IV, V, and VI (Oven-Aging). Times of failure were measured on PP films (6 mil) stabilized with 0.1% (w/w) of the chainbreaking antioxidants IV, V, and VI with and without dilaurylthiodipro-pionate (DLTDP) or distearylthiodipropionate (DSTDP) (0.25%). In Table II the results obtained at 140°, 120°, and 80°C are summarized. Moreover the synergistic action (S.A.) was calculated. 

Influence of the Thioether Structure on the Synergism between Phenyl-Substituted Phenols and / -Activated Thioethers (Oven-Aging). 

From the preceding section it could be concluded that among the variety of phenyl-substituted phenols, 4-stearoxy-2,6-diphenylphenol (Vile) proved to be the most powerful chain-breaking antioxidant when used in combination with -activated thioethers. 4-Stearoxy-2,6-diphenylphenol is used now as the chain-breaking antioxidant and tested with a variety of -activated thioethers. 

As an intermediate experiment between the model reactions in o-di-chlorobenzene and the oven-aging tests of PP stabilized with combinations of phenyl-substituted phenols and -activated thioethers, the behavior of 4-methoxy-2,6-diphenylphenol (Vila) and / ,/ -diphenyldiethylsulfide was studied in PP under realistic processing conditions and in aging of the sample. 

Phenyl-Substituted Phenols (V). 2,4-Di-octadecanoxy-6-chloro-s-triazine (16). To a solution of 18.4 g of cyanuric chloride (0.1 mol) and... 

Phenyl-Substituted Phenols VI. VIb. A solution of 1.85 g (0.01 mol) of cyanuric chloride in 6 mL of dry acetone was added to 6 mL of ice water, and the mixture was cooled (0°-5°C). Then 5.5 g (0.02 mol) of / -mercaptopropionic laurylester was added dropwise, while stirring and keeping the temperature at 0°-5°C. After adding the / -mercaptopro-pionic laurylester the temperature was raised to 20°C, and a solution of 1.1 g of Na2C03 in 4 mL of water was added dropwise. Then the temperature was raised to 40°C (C02 ). After 2 hr the reaction mixture was poured into ice water and was extracted with 3 x 50 mL of dichlorometh-ane, washed with water, and dried over MgS04. After removing the solvent, a white solid was obtained. Recrystallization from hexane gave... 

Phenyl-Substituted Phenols VII. General procedure. To a solution of 26.2 g (0.1 mol) of 2,6-diphenylhydroquinone(III) in 200 mL of the appropriate alcohol there was added, while stirring, 5 mL of concentrated sulfuric acid over 3 hr. After additional stirring for 1 hr at 65°-130°C, depending upon the alcohol used, the reaction mixture was diluted with 200 mL of chloroform and was washed with water. After evaporation of the chloroform, a light yellow syrup was obtained which gave the 4-alkoxy-2,6-diphenylphenol after crystallization from a hexane/toluene mixture (95 5). Vila, yield 87% mp 67.6°-68.1°C Vllb, yield 72% mp 89.1°-89.9°C Vile, yield 55% mp 34.2° 35.3°C Vile, yield 84% mp 56.9°-60.3°C. The identity and purity of the phenyl-substituted phenols... 

Oxygen-Uptake Measurements. Combinations of phenyl-substituted phenols and / -activated thioethers were tested in unstabilized isotactic PP according to the method described by Pospisil, Taimr, and Kotulak (20). Powdered PP (1.000 g) was mixed with 2 mg of the phenol and 5 mg of the thioether. This mixture was homogenized with 5 mL of acetone. The solvent was evaporated carefully in vacuo at 40°C and the sample was placed in a tube connected witn a gas burette filled with oxygen. The oxygen uptake was measured at regular time intervals at 180°C (see Table I). 

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