CONTRIBUTION OF SONIC EFFECT ON THE STEREOISOMERIZATION AND ON THE EPOXIDATION OF ALL-TRANS-β-CAROTENE

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Abstract
Sonk effects on the stereoisomerization and on the epoxidation of all-trans-[beta]-carotene were evaluated. The sample solution was sonicated using sonic oscillator (20kc/sec, 300 w). When submitted to sonication, all-trans-[beta]-carotene underwent partial trans[forward arrow]cis isomerization. The extent of this phenomenon and its reproducibility were variable depending upon the kind of the solvent and the amounts of the isomers increased when a conventional photochemical or thermal treatment was used together. Apparent sonic effect for isomerization in the chloroform solution of the sample under non-additive and in the darkness reached to ca. 30% of the starting material treated and the highest yield of cis isomers amounted to 55% (neo U 22, neo B 27, neo D 4 and neo E 2%) when the hexane solution of all-trans compound containing catalytic amount of iodine was sonicated under illumination. [beta]-Carotene epoxides were prepared more easily in a short time by the sonic treatment of the hexane solution of [beta]-carotene solution of [beta]-carotene containing perphthalic acid. When perphthalic acid was used 6 times by weight of [beta]-carotene, the sonication gave 5,6-monoepoxide, 5,6,5[image]6[image]-diepoxide and 5,8-monoepoxide in the yield of 26, 4 and 2% respectively, and almost half of the starting material was recovered. Little or no sonic effect was observed when the solution of [beta]-carotene was sonicated during its air- or H2O2-oxidation. [beta]-Carotene epoxides were more stable than their parent hydrocarbon carotenoid, [beta]-carotene.

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