The color centers and free radicals produced in irradiated solid alcohols, ketones, ethers, and other compounds have been examined experimentally by means of optical absorption and EPR spectroscopy to obtain information regarding the products of ionization and the associated electronic processes. At liquid nitrogen temperature these products of electron or x-ray bombardment are stable; however, the color centers are photosensitive and can be bleached both optically and thermally. The alcohols also show an increase in absorption near the characteristic uv bands. Removing the visible color centers increases the EPR hfs, but bleaching in the uv band markedly reduces or changes the hfs. In methanol and ethanol, free radicals are formed with good efficiency requiring about 18 and 12 ev per radical, respectively. Saturation concentrations of 2×1019 and 9×1019 spins per cc were produced in acetone and methanol, respectively. The hfs of ethanol and methanol indicate an alkyl hydrogen is missing from the radicals produced by irradiating these materials. No sign of the atomic hydrogen doublet was observed at liquid nitrogen temperature. Support for the α—β hypothesis was found in the hfs displayed by the irradiated alcohols, paraffins, ketones, and ethers.
The free radicals formed in solid n-propanol by radiolysis were examined by electron paramagnetic resonance (EPR) techniques and compared to radicals in photolyzed propanol-hydrogen peroxide mixtures. Identification of the radicals is based on modifications in the EPR hfs introduced by substituting deuterium for hydrogen at selected positions in the molecules. Radiolysis leads to radical formation by removing a hydrogen atom from the α carbon while photolysis apparently favors hydrogen abstraction from the β carbons. Mass spectrographic analysis of the gas liberated during irradiation gave corroborative evidence regarding the hydrogen atoms; however, the analysis also showed that some hydrogen escaped from other than the α and β carbon positions. The experimental EPR hf spectra are compared to a series of constructed spectra obtained by summing Gaussian absorption curves according to the interactions indicated by the proposed models of the radicals.
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