ACTION OF IONIZING RADIATION ON SIMPLE ORGANIC COMPOUNDS 



scavenger may not capture all the available free radicals. Some of the 

 results (the product distributif)ns) are valid if all free radicals are captured 

 with the same efTiciency, hut there is no evidence to confirm or deny this 

 proposition. The 6'-values determined will depend strongly on the clliciencies 

 of radical capture. 



The exact lifetime of a free radical in solution is not known, l)ut it seems 

 sufficiently long to give reaction with iodine. The activated free radicals 

 would have even longer lifetimes than the non-activated. 



Elliciencies of free radical capture by iodine should be of the order of 

 90 per cent. 



It should also be remembered that the free radicals detected are only 

 those which diflfuse from the radiation track and have become thermalized. 

 Recombinations within the spur cannot be followed in this way. 



The presence of foreign compounds during the radiolysis of hydrocarbons, 

 is responsible for changed effects. There are two types of change, an en- 

 hanced decomposition and a protective action, but both effects are due to 

 energy exchanges in the mixture. 



Enhanced reaction has been found when pentane was irradiated in the 

 presence of silica geP^. The products formed were not increased pro- 

 portionally to the simple irradiation, and this indicates that the exchange of 

 the energy absorbed in the silica, and then transferred, is not a simple 

 exchange. It is quite possible that reactions of this type could occur with 

 the glass walls of the reaction vessels. 



The second effect of the protective action is shown in the irradiation of 

 benzene-cyclohexane mixtures ^^. It has been shown that the mixture acts 

 more like benzene than a mixture. The suggestion is that benzene has a 

 greater capacity for absorbing energy without decomposition, due to the 

 resonating structure of the benzene. There is energy exchange from the 

 cyclohexane to the benzene, where the energy finally appears as heat rather 

 than energy of bond fission. These conclusions have been drawn from the 

 study of gas yields and gas analysis from the radiolysis of mixtures of benzene 

 and cyclohexane. 



From these examples where energy exchange is known to take place with 

 changed effects, it is logical to conclude that in irradiation of simple com- 

 pounds, exchange also occurs between the molecules. During the irradiation, 

 molecules, activated to differing extents are present. Possibly, the different 

 products result from the decomposition of molecules of differing degrees of 

 activation. 



There are other scavengers that have been used® l)ut none have been 

 found to be as convenient as iodine, as iodine is the only scavenger with 

 which the products from different free radicals may be detected. Other 

 scavengers give the total free radicals only. 



From the study of the action of radiation on pentane it is hoped that the 

 different techniques, especially those in which iodine is a scavenger and 

 those with irradiations of the pure liquid, may be combined to give an 

 overall picture. Furthermore, when we see the diversity of products formed 

 from such a simple compound as pentane, we can imagine the multitude of 

 products produced when more complex compounds are irradiated. Indi- 

 cations that every bond in pentane is capable of breakage have been found. 



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