194 ABIOGENIC ORGANIC-CHEMICAL EVOLUTION 



Pasteur were not, in fact, dissymmetric. Pasteur's experi- 

 ments were based on a false conception of the asymmetry o£ 

 motion and magnetic fields. His idea was, however, funda- 

 mentally sound. 



As early as the end of the nineteenth century J. H. van't 

 Hoff^" pointed to the circular polarisation of light as a 

 possible cause of the appearance in nature of dissymmetric 

 substances formed photochemically. For a long time attempts 

 to confirm this idea experimentally did not meet with posi- 

 tive results because those who performed them did not take 

 account of the condition " that one should choose only those 

 reactions which can usually be initiated by the action of the 

 waves of light ".^** 



Success was first obtained in 1929 by W. Kuhn and E. 

 Braun,^^^ who decomposed a racemic ester of a-bromopropri- 

 onic acid under the influence of circularly-polarised ultra- 

 violet light with a wavelength of 2,800 A. These experiments 

 showed that it is possible to obtain an optically active sub- 

 stance from an inactive one without any participation by 

 organisms or products derived from them. In these experi- 

 ments, however, as in many later ones (W. Kuhn and E. 

 Knopf,^" S. Mitchell,^" J. C. Ghosh,"« and others) the 

 optical activity did not, strictly speaking, arise as the result 

 of the synthetic process but was due to the fact that the 

 antipodes making up the racemic mixture decomposed at 

 different rates under the influence of the polarised light. 



The direct synthesis of a dissymmetric substance by irradia- 

 tion with circularly-polarised light was first accomplished 

 by G. Karagunis and G. Drikos^*^ and later by a number of 

 other workers. 



The synthesis by T. L. Davis and J. Ackermann"" is 

 specially interesting to us. By irradiating completely optically 

 inactive original materials with right circularly-polarised 

 ultraviolet radiation (2,535 " 2,539 A) these authors obtained 

 a substance, tartaric acid, as the very antipode which is 

 widely distributed among living things. 



It may now be held that we have complete proof of the 

 presence of circularly- or elliptically-polarised light under 

 natural conditions. This was already established by A. Byk^^^ 

 and has since been fully confirmed. For example, the light 



