Gaseous products from radiolysis

Very few investigations of the radiolysis of nitroalkanes have been reported, and no systematic study of their radiation chemistry has been made. Low molecular weight nitroparaffins were irradiated with y-rays from a cobalt-60 source using dose rates between 0.5 and 2.5 x 10" rad.h and the products analyzed by gas chromatography and mass spectrometry . The yield of gaseous products from irradiated nitromethane was drastically reduced if after a short irradiation, such as is obtained with a linear accelerator, the samples were immediately quenched in liquid nitrogen. Inder these conditions [Pg.668]

As expected, radiolysis products are complex. Apart from Ha, which is the principal gaseous product, these authors have identified saturated and unsaturated hydrocarbons up to Cio- Among them, isodecane is most abundant approximately 50% of the reacting pentane is to be found under this form. 

Radiolysis of liquid cresols under vacuum was found to produce H2 as the main gaseous product the radiolytic yield varied from 0.019 for m-cresol to 0.031 (rmol for the o-cresol. Small amounts of CH4 were also detected. Radiolysis of cyanophenols produced less H2, only ca 0.003 ttmol various yields of CO and CO2, mainly from the ortho isomer, and minute amounts of N2. The difference in the yield of H2 may be due to reaction of hydrogen atoms with the methyl group of the cresols to form H2 as compared with addition to the CN group and to the ring, which do not produce H2. No mechanistic details were derived from these studies. 

A wide range of gaseous products have been identified by Busfield and coworkers (246) on y radiolysis of PMMA at room temperature, which arise principally from a breakdown of the ester side-chains. The principal products and their jdelds G are respectively H2, 0.34 CH4, 0.66 CO, 1.08 CO2 0.68 CH3OH, 0.36 HCO2CH3, 0.69 dimethoxymethane, 0.11 and CH3AC, 0.02. Kudoh and coworkers (250) have measured the yields of H2, CH4, CO, and CO2 on radiolysis at 77 K and report that whereas the hydrogen yields are the same at 77 K and room temperature, those for the other gases are lower at 77 K. This is in accord with the temperature dependence of the observed radical yields (248) and with the mechanical properties (251). 

Concentration of TBP. The rate of TBP decomposition and the yields of major acids G(HDBP) and G(H2MBP) increased with the concentration of TBP (8, 85, 88). On the other hand, the yield of gaseous radiolysis products coming from the diluent decomposition decreased with an increasing fraction of TBP (88, 96). 

The radiolysis of water produces hydrated electrons (e q, G = 2.9), hydrogen atoms (G = 0.55) and hydroxyl radicals (G = 2.8) which react with the solute molecules. In addition, the radiolysis of aqueous solutions also yields H202 (G = 0.75), gaseous hydrogen (G = 0.45) and hydronium ions (H30+, G = 2.9). In most cases the molecular products do not interfere with the reactions of the radicals. To study the reaction of one radical with the solute without interference from other radicals, scavengers for the other radicals should be added7-10. 

Table 2 gives the yields of the various products in Co radiolysis of gaseous cyclopropane obtained by the several workers. It shows a good agreement of the yields of the main products obtained in the various studies. However, there are some disagreements, e.g. for propane or isobutane formation. The controversy concerning the G-value for propane formation can be explained if von Bunau and Kuhnert s system included small amounts of alkanes which were found to increase the yield of propane from 0.5 to 1.0. 

Radiolysis and photolysis products were analyzed by injecting samples into an F M gas chromatograph provided with a flame ionization detector. A 1/4-inch o.d. Teflon column 2 ft. long, packed with Porapak Q, was used to separate the components from the column in a reasonably short time. In some cases fractions were trapped out from the helium stream at the column outlet and analyzed on a C.E.C. 21-103C mass spectrometer. Conventional high vacuum techniques were used in handling all gaseous samples and products. 

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