RADIOLYSIS OF ALKYL HALIDE-HYDROCARBON SOLUTIONS AND SZILARD-CHALMERS CHEMISTRY OF ALKYL HALIDE-HYDROCARBON SOLUTIONS
Work was carried out to obtain a better understanding of the interactions occurring between solvent and solute during irradiations of alkyl halide-hydrocarbon solutions. This was done by investigating the chemical fate of several alkyl halide solutes which were labeled with either I/sup 131/ or C/ sup 14/ and whose concentration in pentane solutions was varied. Using optical spectrometry and gas chromatography, the products of the gamma radiolysis were identified and their yields determined. In dilute solutions of methyl iodide in pentane, the observed products, included methane, ethane, propane, n-butane, n- hexane, 2- and 3-methylpentane, and ethyl, n-propyl, n-amyl iodides, and 2- and 3- iodopentane. The G values of the hydrocarbon products increased with increasing methyl iodide concentration from 0 to 0.75 mole%, and were constant from 0.75 to 2.3%, the highest concentration studied. The G values for iodinated products formed in the radiolysis of pentane soluttons were equal for CH/sub 3/I and C/sub 2/H/sub 5/I solutes at concentrations of 1.2%, and appeared to be constant from 1 to 10% when ethyl iodide was the solute. The amount of methane produccd in methyl iodide-pentane solutions was about fifteen times the yield of the remaining hydrocarbon products. Its yield was decreased by 95% by the addition of molecular iodine. Using iodine tagged with I/sup 131/ as a radical scavenger, it was found that the addition of an alkyl iodide or bromide at about one mole per cent to iodine-pentane solutions greatly increased the yield of the corresponding alkyl radical, while the yield of the remaining radicals decreased by approximately 30%. The addition of n-propyl chloride to an iodine-pentane solution did not significantly change the yield of any of the radicals formed by ionizing radiation. Iodine was produced in the radiolysis of ethyl iodide-- pentane solutions at concentrations above about 5% ethyl iodide. With increasing concentration, G(I/sub 2/) increased linearly with the fraction of the total energy absorbed by ethyl iodide. G(HI) in a solution of 2.0% ethyl iodide in pentane was less than 0.04. These observations are consistent with the conclusion that dissociative electron capture by the alkyl halide is an important process in the radiolysis of alkyl halide--hydrocarbon solutions, the electrons being formed from the hydrocarbon by ionizing radiation. The radicals formed by this dissociation can combine with other radicals or attack the solvent to form the observed products. In the radiolysis of methyl iodide-pentane solutions, methane appears to be formed by the abstraction of hydrogen from pentane by methyl radicals produced by dissociative electron capture. This production is inhibited by iodine due to the scavenging of methyl radicals to form methyl iodide. The fact that n-propyl chloride added to iodine-pentane solutions does not increase the radical yield as do iodides and bromides is in agreement with the low efficiency reported in the literature for electron capture by chlorides. The I/sup 127/(n, gamma )I/sup 128/ process in alkyl iodidepentane solutions yields a large fraction of the I/sup 128/ in the form of the alkyl iodide solute. Using gas chromatography, was found in ten products including methyl, vinyl, ethyl, isopropyl, n-propyl, sec-butyl, n-amyl iodides, and 2- and 3-iodopentane. In the neutron activation of ethyl iodidepentane solutions containing scavenger iodine, a larger per cent of the organic I/sup 128/ activity was also found in the form of ethyl iodide. Solutions of n-propyl chloride in pentane did not show a large fraction of Cl/sup 38/ activity as npropyl chloride. The formation of the products containing recoil atoms can be explained by reactions of the recoil atom with radicals produced by ionizing radiation.
- Research Organization:
- Univ. of Wisconsin, Madison
- NSA Number:
- NSA-16-022178
- OSTI ID:
- 4814988
- Journal Information:
- Dissertation Abstr., Vol. Vol: 22; Other Information: Orig. Receipt Date: 31-DEC-62
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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