Bromine reactions activated by 79Br(n,7)80Br, 81Br(n,7)82Brm + 82Br, and 82Brm(I.T.)82Br nuclear transformations were studied in halomethanes as functions of mole fraction of Br2, phase, density, and intermolecular distance. Gas phase systematics coupled with the density and mole fraction of Br2 studies demonstrate the existence of systematic trends in the condensed phases as evidenced by the Richardson-Wolfgang effect. A definitive difference due to activation that is independent of system and suggests the importance of caging at higher densities is shown by the variation of total and individual organic product yields with density. The study of total organic product yield vs. intermolecular distance provides both a means of separating cage and molecular reactions and suggests the importance of molecular properties in the caging event.

Publication costs assisted by the U.S. Energy Research and Development AdminlstratlonThe reactions of lZsI activated by radiative neutron capture with acetylene occur primarily through an addition channel forming an electronically excited reaction intermediate. Acetylene is unlike olefins in that no photochemical addition occurs under conditions simulating sample handling. In an excess of gaseous acetylene, at l atm 14.9 f 0.6% of lZsI is stabilized as organic activity to the following extent: CH3I 0.49%, CH& 0.70%; C2H31 0.40%, CzH5I 9.30%; i-C3H7I 2.71%; CH~CH~CHICHS 1.10%, CH3(CH2)3I 0.20%. The effects of rare gas additives in moderating lZ8I with gaseous CzH2 were determined in an effort to ascertain the nature of the activation process. Only the C2H51281 yield is decreased by the presence of rare gases, suggesting that both hot lZsI ions and thermal I+(lD2) and other excited ions are involved in the primary addition to acetylene. The gas to condensed phase studies showed a depletion of all C1, vinyl iodide, Cs, and C4 128I-labeled products; where the only product observed in high pressure gas and condensed phase systems was C2H51281. A reaction scheme is proposed which postulates the existence of an excited complex reaction intermediate. The properties of the proposed complex are compared qualitatively to those predicted by RRKM, "caged" complex, and caging radical theories of enhancement yields.

The gas to condensed phase transition technique has been used to study the iodine-128-ethane system. Total organic product yields were found to range from 1.1 (1 atm gas) to 61.2% (-23 °C liquid). Various molecular and enhancement reactions are evaluated using available data and a comparison is made among ethane and other two carbon hydrocarbons.

Reactions of high energy iodine with butene-1 have been found to yield six organic products. Additive studies show that of 21.4% total organic product yield at 1 atm, the majority is the result of high energy reactions, many radical in nature. The gas to condensed phase transition shows a typical rise in all organic products except vinyl iodide. Analysis of all available data suggests that the products formed in the reactions of iodine with butene-1 arise from a diverse and complex series of product formation routes; however, greater than 70% of the organic products formed at 1 atm are the result of preferential site attack by iodine at or near the double bond.

Reactions of Iodine with OlefinsThe Molar Extinction Coefficients for H2NC(-0)ÑH and HÑCN. Figure 4c summarizes the absorption spectra and the molar extinction coefficients for the radicals produced by the reaction of hydroxyl radicals with cyanamide. They are mainly derived from the experimental data obtained with 4.6-20 krd per pulse and with 0.5 M NH2CN solutions (pH 5). For the computations of the free radical concentrations, the reaction scheme included reactions 1-8, 12-16, and 20-22. Concluding Remarks(1) The results obtained in this work offer a fairly complete picture of the early stages of the radiolysis of NH2CN in aqueous solutions at pH 5. When the proposed reaction scheme is used in computer simulation of the reaction mechanism, the computed rate curves agree with the experimental ones within 15%. This is considered a fair agreement because of the large range of experimental conditions under which the testing was carried out (1.85-26.7 krd/pulse, 0.025-1 M NH2CN).(2) This study shows that the cyano group in NH2CN is the main point of attack by hydroxyl radical, hydrogen atom, and hydrated electron, as was the case for the >C-CN molecules and various cyanides previously studied.