Some electron-gain and electron-loss reactions of molecules and ions in condensed phases

In the presence of the compounds having the long-pair of electrons available for bonding, electron-loss radicals can stabilize themselves by forming 3-electron bonds. Primary loss-centers can be detected by ESR spectroscopy. When a compound is exposed to electrons, it may dissociate by a variety of routes (dissociative electron capture), and solvation may play a significant role. ESR evidence shows that unpaired electrons become more strongly localized on the 2 atoms directly in the sigma bond than they are in the parent radical. In some systems, there is competition between the electron capture into a localized sigma orbital and that into a delocalized π orbital. Important examples are halouracils. The electron capture into the C-halogen sigma level is extensive for bromide and iodide, but for chloride, only the capture into the π level was detected. Electron-loss from organic halides has not been widely studied, since R-halide+ cations are orbitally degenerate and not detectable by ESR spectroscopy. Electron capture causes dissociation to give R and halogen-. The electron capture by metallo-enzymes (oxyhemoglobin and myoglobin, xanthine oxidase, hemocyanin) is discussed on the basis of the ESR studies on the effect of ionizing radiation on the organic derivatives of biological significance. (Yamashita, S.)