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THE ACTION OF IONIZING RADIATION 

 ON SIMPLE ORGANIC COMPOUNDS 



K. H. Napier and J. H. Green 



The Department of Radiochemistry, University of New South Wales, 



Kensington, N.S.W. 



INTRODUCTION 



Interest has been taken in the action of ionizing radiation on organic 

 compounds ever since radio-active inaterials have been used. Lind^, in a 

 series of papers in 1926, reports experiments on the reactions of various 

 hydrocarbons in the presence of radon which is decomposing to give off a- 

 particles. Various degradative and polymeric compounds were found. 



Interest has been revived in this study as radiation sources have become 

 readily available over the past ten years. The accent of these studies has 

 however changed. Whereas Lind was satisfied in reporting that he found 

 polymeric compounds, now we want to know what these polymeric com- 

 pounds are and how they are formed. 



But the simple irradiation of pure organic compounds gives results that 

 are difficult to interpret, as many compounds are formed and their analysis 

 is difficult. Dewhurst- has found 16 products from the radiolysis of ;i-hexane, 

 with analysis by gas chromatography, which is the most useful technique 

 to date. Hydrocarbons from C^ to C^g, both straight and branched chain, 

 were formed. Other products could have been present, but they were not 

 identified. Mechanisms can be put forward to explain these products, but, 

 when it is possible for any bond in the original compound to be broken and 

 when secondary reactions and radical combinations can occur, a quantitative 

 approach is difficult. 



A study of the primary processes involved in the radiolysis is more informa- 

 tive, and enables predictions to be made. This is important when synthesis 

 by ionizing radiation is contemplated because this is the field in which 

 radiation will prove useful in the future, especially as larger and larger 

 sources become available. 



When radiation acts on organic compounds, and the radiation is absorbed, 

 the molecules are activated or ionized. Pentane has been chosen as an 

 example in these studies as it represents the simple hydrocarbons which are 

 the simplest of organic compounds. 



The primary process can be represented as: 



C5H12 > C^Hf^ or C5H+2 (/) 



The next step is for the activated molecule or molecule-ion to lose the 

 excess energy, in coming to a relaxed state, as heat or some other form of 



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