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Chalcones are the starting materials for the biosynthesis of flavonoids. Flavonoids are strong antioxidants, which contain many phenolic hydroxyl group(s). However, the antioxidant activities of chalcones have been little studied. In this study, chalcones with chemical structures resembling natural chalcones were synthesized, and the effects of the hydroxyl group(s) on the A and B rings and the C3 chain connecting the A and B rings were investigated in detail. Hydroxyl group(s) on the B ring inherited the characteristics of p-coumaric acid as a precursor of chalcone, if the groups were located on 2-and/or 4-positions to the C3 chain, and showed strong antioxidant activities. The 2'-hydroxy group of the A ring cooperated with the carbonyl group on the 1'-position to provide ultraviolet rays absorbing (photo-antioxidant) activity. The carbon _ carbon double bond in the C3 chain, connecting the A ring with the B ring in a conjugated system, enhanced both antioxidant and photo-antioxidant activities. The obtained information was used in the molecular design of new polymer additives.

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The oxidation of cumene and acrolein was carried out using metal polyphthalocyanines as a catalyst. The catalyst activated an oxygen molecule to form a phthalocyanine–O2 complex, which then abstracted the hydrogen atom of a reactant to initiate the oxidation. The catalyst had no effects on the decomposition of cumene hydroperoxide, formed selectively in the oxidation of cumene. The addition of a small amount of pyridine induced a drastic shortening of the induction period as well as a considerable increase in the oxidation rate. The initiation mechanism assumed on the basis of findings on the desorption of oxygen from the catalyst and on the effect of pyridine was confirmed by a kinetic study of the homogeneous liquid-phase oxidation of acrolein.

The kinetics of the inhibition of the autoxidation of several hydrocarbons by a number of zinc dialkyldithiophosphates and by zinc isopropylxanthate and zinc diethyldithiocarbamate have been studied at 30' and at 50'. The oxidations were generally auto-retarding but initial rate measurements showed that these compounds trapped peroxy radicals and allowed rate constants for this process to be calculated. Rate constants for the reaction of t-butylperoxy radicals with these compounds have been measured by a kinetic e.p.r. method in the temperature range 0' to -90'. Extrapolation of the e.p.r. data to the temperatures of the inhibition studies showed that the various experimental procedures yielded results in satisfactory agreement with one another.It is suggested that the reaction of peroxy radicals with zinc complexes involves reaction at the metal center either by an electron transfer or an SH2 process.Les cinetiques d'inhibition de I'auto-oxydation de plusieurs hydrocarbures par un certain nombre de phosphates de dialkyldithio zinc, d'isopropylxanthate de zinc et de diethyldithiocarbamate de zinc, ont etC CtudiCes h 30'et a 50'. Les oxydations sont generalement auto-retardees rnais les mesures de vitesse initiale montrent que ces composes piegent les radicaux peroxy et permettent ainsi le calcul des constantes de vitesse pour ce processus. Les constantes de vitesse pour la reaction des radicaux I-butylperoxy sur ces composes ont kt6 mesurees par une methode cinetique r.p.e. dans I'intervalle de temperature de 0' a -90'.L'extrapolation des donnees r.p.e. aux temperatures d'etude de I'inhibition montre que tous les divers procedes experimentaux donnent des resultats en accord satisfaisant.On a suggCrC que la reaction des radicaux peroxy sur les co~nplexes de zinc implique une reaction sur le centre metallique soit par un transfert d'electron soit par un processus SH2.

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