283 



li(|iiid> an- used as solvents, namely, so long as they do not 

 tln-msrl\v> take part in the reactions. This may also be concluded 

 from the fxjxTiments of B re dig and his collaborators: thus 

 1 i g and B a 1 c o m l ) stated, that d- and l-campho-carboxylic 

 (H -iiis are split into camphor and carbon-dioxide equally quickly 

 \\ lu n dissolved in d-, or in l-limonene. But, as we shall see later, 

 as soon as optically active bases (like quinine, quinidine, nicotine, 

 etc.) are used in this case as solvents, which undoubtedly take 

 part in the reaction, combining with the acids to form inter- 

 mediate compounds, - - the differences in reaction-velocity of 

 both antipodes can clearly be demonstrated, as we shall see in 

 the following paragraphs. 



7. Thus, if the components A and A' really combine with 

 the active molecule B, a difference in reaction-speed will most 

 probably be found, notwithstanding the equal affinity of both 

 antipodes towards B, because there is some guiding influence of 

 the pre-existing dissymmetry of B in the formation of the com- 

 pounds AB and A 'B. 



It is on this principle that the new method of fission of race- 

 moids, proposed in 1899 by Marckwald and Me. Kenzie 2 ), 

 was founded; and it is this difference in the velocity of forma- 

 tion, as a consequence of the directing power of a pre-existing 

 dissymmetry, which doubtless gives the explanation of the apparent 

 difference between artificial and natural synthesis, with which we 

 shall now have to deal somewhat more in detail. 



Indeed, in the preceding chapter we have had occasion to see 

 how in the laboratory optically active substances can only be 

 obtained from inactive materials, if one of the special methods 

 of fission proposed by Pasteur is suitably applied. If in artificial 

 synthesis we start with optically inactive materials, we only can 

 get optically inactive compounds, - - even when a new asymmetric 

 carbon-atom is produced in the molecule under investigation. 



Our synthetic products are always racemic substances or exter- 

 nally compensated mixtures; and the explanation of this has 

 always been given by drawing attention to the fact that in 

 reactions, in which only symmetrical causes play a role, enantio- 

 morphously related molecules must have the same mechanical 



1) G. Bredig and R. W. Balcom, Zeits. f. phys. Chemie 41. 740. (1908). 



2) W. Marckwald and A. Me. Kenzie, Her. d. d. Chem. Ges. 82. 2130. (1899). 



