Active Species. of γ -Irradiated Vinyl Acetate and Their Changes on Irradiation of Visible Light

Abstract

Free radicals produced by γ -irradiation of vinyl acetate in the solid have been studied with electron spin resonance (ESR) and the changes of these radicals on the visible light irradiation have been also examined. An oriented solid of vinyl acetate was prepared for ESR measurement by the solidification of vinyl acetate around an aluminum rod at -196° C or -117° C and with subsequent γ -irradiation (dose; 8 X 106 rad) at -196° C. The oriented crystalline solid prepared at -117° C gives an ESR spectrum consisted of a singlet and additional adsorptions in the dark at -196° C. After irradiation of visible light for 10 minutes, ESR spectra of oriented crystalline solid exhibit a distinct hyperfine structure and a definite anisotropy on the rotation of the solid in the dc magnetic field. These spectra consist of a quartet (A1 =12.5 G), an anisotropic triplet and an equivalent four lines (A1=103 G, A2=16 G), corresponding to the radicals, CH, COO3COO., . H2COOCH=CH2 and CH2=C H, respectively. The prolonged irradiation with visible light for 300 minutes yields the apparent five lines, consisted of a pair of triplet (A1=10 G, A2=20 G) and the above-mentioned triplet corresponding to the radicals CH2CHO and CH2COOCH=CH2, respectively. The spectrum of the r-irradiated glassy solid prepared at -196°C consists of strong four lines which is confirmed to be isotropy and of a weak doublet splitted by 120 G, corresponding to vinyl radical. Irradiation of the glassy solid with visible light for 30 minutes gives a sharp quartet (A1=23 G) assigned to CH3. produced by the photolysis of CH3C00., A broad triplet (A1 =22 G) becomes to be observable on elevation of the temperature to -160° C and remains up to -100° C. This triplet is assigned to CH2COOCH= CH2. In conclusion, both the crystalline and the glassy solids produce the same radicals on γ -irradiation.