Shoji Shida

Effects of Gases on Irradiated Polyvinyl Chloride as Studied by Electron Spin Resonance

The radicals produced by gamma irradiation of polyvinyl chloride powder in various gases and in vacuum are observed by electron spin resonance. Different patterns are observed for the irradiation in vacuum, air, and sulfur dioxide. No electron spin resonance absorption is obtained by the irradiation in nitrogen oxide, halogens, and hydrogen sulfide. The recombination reaction velocity of the radical produced in vacuum is measured at different temperatures to get the activation energy 38 kcal/mole.

Fragmentation of excited molecules and ions in the radiolysis of hydrocarbons

Abstract A survey is given of recent studies of the primary CH and CC bond dissociations of excited molecules and ions in the gas- and liquid-phase radiolysis of hydrocarbons, which have been mainly carried out by the product analysis method. In the CC bond dissociations evidence has been presented for the fragmentation of the excited parent ion, while in the CH bond dissociations attention has been focused upon an important role of hot hydrogen atoms in the hydrogen formation. A theoretical treatment of highly excited hydrocarbon molecules involving super-excited states is also described.

Electron Spin Resonance Studies of Gamma‐Irradiated Single Crystals of Sucrose

The electron spin resonance of gamma‐irradiated single crystals of sucrose has been measured at 9400 Mc/sec for various orientations in the magnetic field. The variations of the resonance with angle were greatest for rotation of the crystal about its b axis, which was kept perpendicular to the magnetic field. The anisotropic hyperfine structure was observed to vanish when the magnetic field is applied perpendicular to the (b, c) plane. It was ascertained that the radical formed is the type X—CH–Y, which had been proposed by Williams et al. from the data obtained from the polycrystalline samples.

HYDROGEN FORMATION IN THE RADIOLYSIS OF LIQUID n-BUTANE.

The effects of a radical scavenger (C2H4) and electron scavengers (N2O or SF6) on hydrogen formation in the radiolysis of liquid n‐butane at room temperature have been studied. Further, the isotopic composition of the hydrogen from n‐C4H10–n‐C4D10, n‐C4H10–n‐C4D10—0.3M N2O, and n‐C4H10–n‐C4D10—0.15M C2H4 mixtures has been measured, and the ratios of unimolecular to bimolecular hydrogen formation determined for each mixture. Combining these results, the yields of six primary processes by which hydrogen is formed have been determined separately with the results that G (thermal hydrogen atom), G (hot hydrogen atom), and G(molecular hydrogen) are, respectively, 0.7, 1.4, and 0.6 by direct excitation and ionization and 0.5, 0.6, and 1.0 by neutralization, with probable errors ± 0.2. It is noticeable that the largest contribution is from hot hydrogen atoms produced by direct excitation and ionization.

PRIMARY PROCESSES OF HYDROGEN FORMATION IN THE GAS- AND LIQUID-PHASE RADIOLYSIS OF PROPANE.

The yield of hydrogen formed in the gas‐ and liquid‐phase radiolysis of propane has been measured in the presence of a “radical scavenger” (C2H4) and an electron scavenger (N2O or SF6). Further, the isotopic compositions of the hydrogen formed in the gas‐phase radiolyses of C3H8–C3D8, C3H8–4 mole % SF6–C3D8, and C3H8–4 mole % C2H4–C3D8 mixtures and also those in the liquid‐phase radiolyses of C3H8–C3D8, C3H8–0.4M SF6–C3D8, and C3H8–0.2M C2H4–C3D8 mixtures have been measured to determine the unimolecular fraction of hydrogen for each mixture. Combining these results, the yields of six primary processes by which hydrogen is formed have been evaluated. The results are that for the gas‐phase radiolysis G (thermal hydrogen atom), G (hot hydrogen atom), and G (unimolecular hydrogen) are, respectively, 2.5, 0.9, and 1.4 by direct excitation and ionization, and that G (thermal hydrogen atom and hot hydrogen atom) and G (unimolecular hydrogen) are, respectively, 1.9 and 0.7 by neutralization. For the liquid‐phase ...

ESR Studies of Carboxylic Acid- and Ester-Radical Anions Produced by γ-Irradiation at 77°K

A series of monocarboxylic acids and esters have been γ-irradiated at 77°K, either pure or in the rigid matrix of 2-methyltetrahydrofuran, and the products have been examined by ESR spectroscopy. The spectra obtained in the pure state showed that the primary paramagnetic species in each case is the corresponding radical anion, (Remark: Graphics omitted.). In the rigid matrix, these characteristic spectra have been obtained after illuminating the γ-irradiated sample with visible light at the expense of the spectra of trapped electrons. When ultraviolet light was used for the illumination, the spectra of the radical anions disappeared, but instead appeared the spectra of the radicals produced by the decomposition of the radical anions. The latter spectra were almost the same as those obtained by the direct photolyses of acids and esters.

Mercury Photosensitized Polymerization of Acetylene

An investigation has been made of the mercury (3P1) photosensitized polymerization of acetylene. Benzene was found in the reaction products in addition to polymer and hydrogen. Effect of acetylene pressure and light intensity on the rate, effect of pressure on the formation of hydrogen and benzene, and effect of temperature on the rate of benzene formation were studied. The fraction of acetylene reacting to form benzene was constant at 0.29 in the range of the acetylene pressure studied. The quantum yield of the over‐all reaction was 4.8 including the yield of benzene and 4.3 excluding it. The reaction mechanism is discussed.

Electron‐Spin‐Resonance Studies of DPPH Solutions

The effects of impurities on the ESR of DPPH in various solutions were studied. The broad quintet spectrum usually obtained with DPPH solutions becomes well resolved after dissolved gases are removed. Addition of tertiary hydroperoxides to DPPH solutions gives a triplet spectrum, which further splits into 17 lines after subsequent degassing in the case of t‐butyl hydroperoxide. From an analysis of this spectrum, a determination was made of the spin‐density distribution of the unpaired electron in a species electronically analogous to biphenylaminium ion.An aerated DPPH solution of xylene loses its paramagnetic nature in time, but regeneration of the quintet ESR spectrum of DPPH is observed if this solution is mixed with the so‐called lophine‐x compound solution kept in the dark, and then irradiated by sunlight. The interpretation of this phenomenon is that the lophine‐x compound, when irradiated by sunlight, has an odd electron which shifts onto the nonparamagnetic DPPH—O2 reaction product regenerating DP...

The Radiolysis of Liquid cis -2-Butene

The radiolysis of cis-2-butene has been studied in the liquid phase at room temperature. (1) The major products (and their G-values) were hydrogen (1.02), n-butane (0.83), 1-butene (0.40), trans-2-butene (2.29), C8 hydrocarbons (2.30), and higher polymers, the G-values being independent of the total dose. Small amounts of C1∼C3 and C5∼C7 hydrocarbons were also formed. The hydrogen and the lower hydrocarbons except for n-butane were found, by using p-benzoquinone as a radical scavenger, to be produced for the most part through the molecular mechanism. (2) The addition of benzene, naphthalene, and anthracene to liquid cis-butene have remarkable effects on the formation of trans-2-butene; thus, the cis-trans isomerization increases at a lower concentration of additives, while it decreases at a higher concentration of additives. The radical scavenging effect cannot explain these results. From a comparison of the experimental results with the ionization potentials and electron affinities of aromatics, it has b...

Behavior Of The Free Radicals Trapped In Gamma-Irradiated Compounds Which Contain Hydrogen Bonds

A series of experiments was performed which suggest that the nonreactivity of gaseous scavengers with free radicals in certain irradiated compounds is not due to inherent free radical stability but to a network of intermolecular hydrogen bonds which prevents penetration by gases. These experiments, performed on polyvinyl alcohol, cellulose, starch, arabinose, ribose, xylose, glucose, fructose, sorbose, galactose, sucrose, cellobiose, lactose, inulin, and glutamic acid demonstrated that free radicals in these compounds, although inert to gaseous scavengers, decay rapidly near the melting point or in the presence of water and react with monomers in presence of water. (D.L.C.)