308 



Marckwald's process is in reality nothing but Pasteur's second 

 fission-method of racemoids l ). 



They compare the reaction with the case in which ordinary 

 racemic acid was first resolved by brucine, and then the less soluble 

 tartrate obtained was reduced to brucine-malate: in this case, after 

 saponification, undoubtedly an optically active malic acid should be 

 found. However, if Marckwald had heated the originally ob- 

 tained mixture of the brucine-salts immediately, and in such a 

 way that heating was stopped before the splitting-off of carbon- 

 dioxide was fully completed, he undoubtedly would have found 

 an excess of the left antipode in the residue, after the brucine 

 was removed from it. 



An attempt of Marckwald and Meth 2 ) to render optical 

 activity to ethyl-a-chloro-phenyl-acetate by heating it with two 

 molecules of brucine, and to isolate the unattacked ether from 

 the reaction-mixture, had no - positive result. But when the 

 amide-formation was used, the velocity of which, according to 

 Menschutkin's investigations, is to a high degree dependent 

 on the chemical constitution of the reacting molecules, they found 

 that there was a considerable difference in velocity, if l-menthyl- 

 amine and racemic mandelic acid were used in the process. Indeed 

 the non-attacked acid appeared to be laevogyratory, and, therefore, 

 the ratio of the velocities V d : Vi was about: 0,86 in this case, 



If a-phenyl-ethyl-amine: C 6 H 5 .CH.(NH 2 ).CH 3 , was heated with 

 l-quinic acid at 165 for 4| hours, and if the quinate of this base, 

 before being transformed into amide, was decomposed by NaOH, the 

 base finally obtained appeared to have an excess of about 3% of 

 the dextrogyratory component. The ratio of the velocities, at which 

 combination with the laevogyratory acid took place, was here : 

 V d : V l = 0,88. 



The velocity of racemisation of two compounds of the same 

 optically active base with a left-, or right-handed acid, will also 

 appear to be different, if they be heated above their racemisation- 

 temperature. 



1 ) Another explanation of this reaction was given by E. Erlenmeyer Jr., by 

 means of his theory of" asymmetrical induction" ; cf. : Bioch. Zeits., 97, 218, (1919). 

 For example, it was demonstrated, that this synthesis may be performed as well 

 by the aid of d-tartaric acid, instead of brucine; cf. : loco cit., p. 242, 243. 



*) W. Marckwald and R. Meth, Ber. d. d. Chem. Ges., 38, 801, (1905). 



