236 



as already stated in the case of the complex chromi-oxalates. Nef *) 

 sees a connection between the tendency for racemisation and the 

 binding and loosening of water-molecules from active organic mole- 

 cules containing hydroxyl-groups, under intermediate formation 

 of unsaturated compounds. Another way of explaining this interes- 

 ting phenomenon was indicated by Erlenmeyer Jr. 2 ) by his theory 

 of "asymmetrical induction", developed by this author for the 

 purpose of elucidating the occurrence of optically active isomerides 

 in the case of some ethylene-deriv&tives, and more especially in the 

 case of the isomerism of cinnamic acid. He supposes, that the 

 molecules of an optically active substance have always a directing 

 influence on the molecules of other substances present; they give 

 them such a configuration in space, that the modified molecules 

 come in as great a stereometrical contrast as possible to those of 

 the original active molecules present, so that the directing forces 

 which start from the last ones, may be neutralised in their actions 

 as completely as possible by the forces starting from the induced 

 molecules. It may then easily be understood that in the case of a 

 single optically active substance, final equilibruim will be reached, 

 when half the number of molecules originally present are converted 

 into their optical antipode. We will return to Erlenmeyer 's 

 views more in detail, when dealing with the isomerism of sub- 

 stituted ethylene-deriv&tives in general (see pag. 268). 



Von Halban 3 ), and also Frohlich and Wedekind 4 ), have 

 demonstrated by means of kinetic measurements, that in the case of 

 optically active derivatives of pentavalent nitrogen, autoracemisation 

 is, indeed, intimately connected with an intermediate detachment 

 of groups, and their successive recombination with the plurivalent 

 central atom. Here the active substance undoubtedly appears to be 

 decomposed into a tertiary amine and an alkyl-halogenide, until a 

 dynamical equilibrium is reached. It is easily understood, therefore, 

 that the velocity of racemisation in these cases appears to be a con- 



1) J. U. Nef, Ann. der Chemie, 335, 191, (1904); Cf. also: O. Rothe, Ber. 

 d. d. Chem. Ges., 47, 843, (1914); P. Pfeiffer, ibid., 47, 1586, (1914). 



2) E. Erlenmeyer Jr., Biochem. Zeitschr., 97, 198, 231, 244, (1919). 



3) H. von Halban, Ber. d. d. Chem. Ges., 41, 2417, (1908); Zeits. f. Elek- 

 trochem., 13, 57, (1907). 



4) E. Wedekind and E. Frohlich, Ber. d. d. Chem. Ges, 38, 3438, (1906); 

 40, 1646, (1907); E. Wedekind and F. Paschke, Ber. d. d. Chem. Ges, 41, 

 2659, (1908). 



