STUDIES IN EXPERIMENTAL ORGANIC COSMOCHEMISTRY 



J. Oro 



Chemistry Department, University of Houston, Houston, Tex. 



The four most abundant elements in the universe, with the exception of 

 the noble gases, are hydrogen, oxygen, carbon and nitrogen,'"'^ which are also 

 precisely the four major constituent elements of organic compounds and of 

 living matter. Indeed, as has recently been said, "the composition of living 

 matter turns out to be a better sample of the universe than the dead earth."'' 



These four elements exist mainly as atoms and diatomical combinations, 

 such as CN, CH, C2 , CO, NH, and OH, in the atmospheres of relatively cool 

 stars,^'^ including the sun,^ and in interstellar or circumstellar space.^'^-^ They 

 also exist as di- and polyatomic combinations in planets,^"" comets,^-'i^ and 

 meteorites. ^^'^^ Thus, simple and complex compounds of carbon are found 

 widely distributed in the universe. In principle, these compounds will exist 

 wherever the prevailing temperatures are compatible with the stability of the 

 bonds between carbon and the other elements. If the carbon containing 

 diatomic combinations, CN, CH, C2 , and CO, are considered, it is observed 

 that their thermal stability ranges from the low temperatures of interstellar 

 space to the relatively high temperatures prevailing above the surface of stars. 

 In fact, such diatomical combinations have been detected in the atmospheres of 

 supergiant carbon stars at temperatures of the order of 6000° K. at which some 

 of the most thermally stable oxides, namely titanium and zirconium oxides, 

 are dissociated into their metallic ions.' 



Observations bearing on the distribution of simple and complex compounds 

 of carbon in cosmic bodies and on the natural formation of these compounds, 

 form part of a space science which may be called "organic cosmochemistry." 



Because of the limited observational data so far obtained and the importance 

 of the fundamental problems involved ,-'''^^ attempts have been made to follow 

 an experimental approach in this study. As a result of the initial experiments 

 of Garrison et al.p Miller,^" '^^ and the more recent ones carried out in this^- and 

 other laboratories,^^ it has become apparent that processes of organic synthesis 

 which may have occurred in the primitive Earth's atmosphere, or may be 

 occurring in certain cosmic bodies such as comets, can be partially reproduced 

 in the laboratory. These experiments have opened a field of investigation 

 for which the name "experimental organic cosmochemistry" is proposed. 



Models for Organic Synthesis 



Any experimental approach to duplicate an incompletely known natural proc- 

 ess requires the formulation of assumptions about the experimental model to 

 be used. It is recognized that it would be difficult to determine with certainty 

 all the conditions applying to a cosmic model for organic synthesis. However, 

 if it is understood that organic reactions pathways are determined by rather 

 general laws, then it becomes possible to obtain significant knowledge about 

 natural organic synthetic processes even with only partially complete models. 



We have focused our attention on a cometary modeP" primarily because 



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