Primary products and processes in the γ-radiolysis of 2-methyltetrahydrofuran

From a study of the u. v., visible, near i. r. and e. s. r. spectra induced by γ-irradiation at 77°K in glassy MTHF and in glassy MTHF containing various additives and from a study of controlled temperature increases on these spectra, the following conclusions are drawn. (1) The primary products of the radiolysis are electrons (e-) and positive ions (MTHF+) which undergo a rapid ion-molecule reaction to give O CH3 radicals (R⋅). (2) e- can either be trapped in the glassy MTHF matrix or can be captured by either napththalene, ferric chloride, carbon tetrachloride, nitrous oxide or trans-stilbene if these substances are present. (3) The e-T are bleachable by light or heat and disappear independently of the radicals R⋅ without either augmentation of R⋅ or the production of any new radical species. (4) e-T and R⋅ disappear thermally and independently by second-order reactions, the rate constants being Ke- + e-(M-1 S-1) = 1012⋅4±1⋅1 exp ─ [0⋅85 ± 0⋅10 kcal/mole/R(T ─ 75)] and KR˙ + R˙(M-1 S-1) = 1013⋅3±1⋅4 exp ─ [1⋅20 ± 0⋅15 kcal/mole/R(T ─ 75)]. These rate expressions suggest that both reactions are diffusion controlled at low temperatures in the glassy phase. (5) The kinetics of the thermal bleaching of e-T indicate that the electrons migrate distances of about 150 Å from their parent positive ions before being trapped in the matrix. (6) The effect of FeCl3 in reducing the formation of e-T at 77°K and its lack of effect on the thermal bleaching of e-T suggests that the reaction e- + FeCl3 → FeCl2 + Cl- only occurs before the electron is thermalized.