275 



<\, luMv.lv in cases in \\lii. h the atoms and radicals: Cl, Br, OH, 

 and NH Z> when linked directly to the asymmetric .nun. 



re replaced by interchanges; however, as has already been said, 

 the orriuK nee of a change of the optical rotation from 

 t<> neiMtive, or vice versa, is greatly dependent on tin- 

 employed in the transformations. *) 



Fischer 2 ) has made an application of the inversion prod i. 

 by the mutual substitution of Aa/ogdw-atoms and the amtwo-group, 

 for the purpose of obtaining both the antipodes of race DIP 

 polypeptides, as for instance in the case of l-alanyl-glycine. 



A certain, although small number of regularities have been 

 found. Thus the substitution of hydroxyl-groups in hydroxy-acids 

 and their ethers by Cl or Br, is commonly connected with a change 

 of the rotatory effect from positive to negative, and vice versa, 

 if PC/ 5 and PBr 5 be used in the reaction. An exception to this 

 rule which in many cases appears to hold good, was found by 

 G u y e and Jordan 3 ), who showed that the laevo-gyr&tory isobutyl- 

 ether of normal-a-hydroxy-butyric acid: CH 3 .CH 2 .CH(OH).COOC t H 9 , 

 was transformed by PC1 5 into a /a^vogyratory chlorinated, but 

 by PBr & into a dextrogyrate brominated derivative. However even 

 in this case it is by no means certain that these two cases also 

 correspond to a real difference in configuration; for it is quite 

 possible that if both Cl and Br came into the same place in space 

 as the HO-group before occupied, the respective substitution- 

 products would yet have oppositely directed rotations. 



Moreover, in replacing halogen-atoms by hydroxyl-groups, the 

 remarkable difference between the action of Ag z O and KOH, as 

 already stated above, has been repeatedly observed. According to 

 Biilman 4 ) this difference of action is intimately connected wit h 

 the fact that the reaction with silver-compounds goes on very 

 rapidly, while that with potassium-hydroxide on the contrary very 

 slowly. The rapid change would occur without a change of e<m- 



1) Cf. O. Lutz, Ber. d. d. Chem. Ges. 41. 841. (1908); Zeits. f. phys. Chemio, 

 70. 256. (1909). 



2) E. Fischer, Ber. d. d. Chem. Ges. 89. 2895. (1906); 40. 489. (1907 

 also: E. Fischer and K. Raske, Ber. d. d. Chem. Ges. 40. 1051. (19<>: 

 Fischer and H. Scheibler, ibid. 41. 889, 2891. (1908); 42. 1219. (1909); E. 

 Fischer, H. Scheibler and R. Groh, Ber. d. d. Chem C.i-s. 48. 2020. (1916); 

 E. Fischer, Chem. Zeitg. (1910), p. 825. 



3) Ph. A. Guye and Ch. Jordan, Bull, de la Soc. Chim. (3). 15. 495. (1896). 



4) E. Biilmann, Ann. der Chemie, 888. 335. (1911). 





