Application Of Thermal Methods Research Articles

The stereoisomerization of β-carotene epoxides and the simultaneous formation of furanoid oxides

1. 1. When submitted to some thermal or photochemical treatments, β-carotene diepoxide, C 40H 56O 2, and the monoepoxide, C 40H 56O, suffer partial trans → cis isomerization. With this spatial rearrangement a structural rearrangement is competing, viz., the formation of Karrer's furanoid oxides. By means of chromatography a quantitative study of the resulting complex mixture was possible. 2. 2. When epoxide solutions were illuminated in the presence or absence of iodine, much more substance underwent stereoisomerization than conversion to furanoid derivatives. However, the latter process became more important upon the application of thermal methods, especially when crystals were fused for a short time. Contacting hexane solution with alkaline alumina resulted in the exclusive formation of furanoid oxides. 3. 3. β-Carotene diepoxide yielded seven and the monoepoxide gave nine cis forms whose spectral characteristics were studied. Some of these isomers are adsorbed above and some below the corresponding all- trans form. Only neo diepoxide V crystallized.