The thermal cis-trans isomerization of trans-ethylene, d2 has been studied from 450° to 550°C over a pressure range of 0.9 cm to 31 cm Hg in two quartz reactors. The rate is pressure dependent over the entire pressure range. It is concluded that at 0.9 cm the reaction is a homogeneous, unimolecular reaction. A high pressure activation energy of 65 kcal and frequency factor of 1013 sec—1 are deduced. At higher pressures the reaction is sensitized by processes attendant on polymerization, which occurs as a side reaction with propylene as the principal product. The relation of this study to other work on substituted ethylenes is discussed briefly, as well as a few other topics pertinent to the results obtained.

By means of a low-temperature ESR technique, several paramagnetic complexes have been detected during the reaction of aqueous [CoII(CN)5]3- with O2. Of these only [(CN)5CoIII-O-O-CoIV(CN)5]5-, the final oxidation product, is stable in solution. It has a 15-line spectrum resembling that of [(NH3)5CoIII-O-O-CoIV(NH3)5]5+ but more sharply defined and independent of pH. Under very alkaline conditions the first oxidation product detectable by ESR has an 8-line signal, indicating a mononuclear complex, possibly [(CN)5CoIII-O-O]3-. It is an intermediate in the oxidation of [(CN)5CoIII-O-O-CoIII(CN)5]6- to [(CN)5CoIII-O-O-CoIV(CN)5]5- and may reach a high concentration in the presence of 0.5M KOH. Although it may also prove to be the expected mononuclear inter- mediate in the oxidation of [CoII(CN)5]3- to [(CN)5CoIII-O-O-CoIII(CN)5]6-, no 8-line signal is detected until the cyanocobaltate(II) has been consumed. Present in small amount is a mononuclear complex with 16 lines, apparently a by-product. Larger amounts can be formed by reducing [(CN)5CoIII-O-O-CoIII(CN)5]6- with NaBH4 in strong alkali at -20�C.

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The decay of defects in polymethyl methacrylate caused by γ-irradiation has been followed by electron-spin resonance. The samples were irradiated at room temperature and annealed at 80, 90, and 100 �C. Two radical species can be recognized by their different modes of decay. Some attempt is made to identify the chemical groups involved and to explain the decay mechanism.