Strahlenchemische Erzeugung und optische Absorptionsspektren organischer Schwefelradikale in organischen Gläsern bei —196 °C

Abstract

Organic disulfides, mercaptans, sulfides and hydrogen sulfide have been exposed to γ-radiation in glasses of methyltetrahydrofuran or hydrocarbons at -196 °C. Absorptions have been observed which are attributed to either radicals of the type RS· or to addition complexes of these radicals to S-containing molecules or ions (for example to RS-SR- radical ions). In the case of disulfides. the S-radicals were produced by dissociative capture of electrons from the ionization of the glassy solvent. In the case of mercaptans, the sulphur radicals were formed via H-abstraction by free radicals from the radiolysis of the solvent, when the irradiated glasses were slowly warmed up. HS was formed this way in H2S containing irradiated glasses. The electron capture in benzylmercaptan, dibenzyldisulfide, and dibenzylsulfide partially leads to the benzylradical. Several new absorption bands have been observed which are tentatively attributed to negative ions: C6H5SH⊖ from phenylmercaptan (8100 A), C6H5SC6H5 e from diphenylsulfide (broad absorption over the visible range), C6H5CHS⊖ from dibenzylsulfide (~ 3900 A). Carbontetrachloride simultaneously present in the glass was found to inhibit all reactions of free electrons, while the reactions of free radicals during warming up were not suppressed. Glasses of a methylcyclohexane-isopentane mixture containing olefins were found to absorb strongly between 7000 and 9000 A. These absorptions are attributed to positive ions. The absorption of ionized or protonated olefins occurs at longer wave lengths with decreasing number of Η-atoms at the carbon atoms of the double bond. Absorption by positive ions was also observed for diphenyldisulfide (8500 A), and for diallyldisulfide (6840 A). Small amounts of substances which can readily be protonated (such as n-propanol or methyltetrahydrofuran) decrease the intensity of the absorption bands of positive ions.