The photoreactions of molecular complexes composed of O 3 and three 5-membered heterocyclic compounds, tetrahydrothiophene (THT), pyrrolidine (PyD), and thiazolidine (TAD), are systematically investigated using matrix-isolation infrared (IR) and UV−visible spectroscopies. Two visible-light absorption bands appear in the visible spectra obtained for O 3 -THT and O 3 -PyD, whereas four bands are observed for O 3 -TAD, which contains both N and S atoms in the heterocyclic ring. Upon visible-light irradiation, O 3 -THT and O 3 -PyD form their corresponding oxide derivatives, tetrahydrothiophene-1-oxide and pyrrolidine-N-oxide. Although two O 3 -TAD complexes with different photoreactivities are detected, both structures form thiazolidine-1-oxide upon combining with O and S atom in the heterocyclic ring, but not thiazolidine-N-oxide. The mechanism of formation of these oxide compounds can be explained by the stability of the oxide compound in the triplet state formed via the combination of O( 3 P) and the paired ring molecule.
synopsisA study was carried to determine experimentally the crosslinking of irradiated polypropylene by ultraviolet rays in vacuo. Three methods of detecting crosslinking were used: measuring the degree of swelling in decalin at room temperature, measuring the gel fraction in a tetrachloroethylene solution of the irradiated sample, and comparing the infrared spectra before and after irradiation. It was found that as the time of irradiation increases, the degree of swelling decreases, whereas the gel fraction in tetrachloroethylene solution increases. This shows that the crosslinking reaction proceeds with time. On the other hand, the infrared spectra of the irradiated sample remained almost unchanged, which shows that different bond species can hardly be formed by irradiation in vacuo. From these facts it may be concluded that the measurements amply confirm the hypothesis. Furthermore, it is demonstrated that ash residue in polypropylene plays an important role in photocrosslinking; that is, the photochemical primary proccss of the reaction is the absorption of light by the ash residue.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.