235 



at present be denied, as we do not know anything as to how the 

 rlu mi( ,il ii lives between tin- Mibstitutes act, and such a contest of 



trai-tin.n and n-puKing forces may be imagined, which would exa. tlv 

 produee tin- iathtr strange and certainly very rare arrangement 

 een in this connection. 



It will be clear from this that in each of both cases supposed, 

 tin plurivalent central atom would be only partly asymmetric, if the 

 word i^ used in the meaning of Van 't Hoff's theory: for in the 

 case first mentioned, the non-superposable arrangement exi-t-. 

 but not the contrast in chemical nature of the asymmetrically arran- 

 ged substitutes; in the second case, the chemical differences between 

 the substitutes, as postulated by Van 't Hoff and Le Bel, are 

 present, but the arrangement of the whole is in this hypothetical 

 molecule such as to make the occurrence of two non-superposable, 

 isomeric molecules impossible here. The last case may be almost 

 accidental, but of the first several instances are now known and 

 have been already sufficiently studied, as we shall soon see. And 

 in this case it has indeed been fully confirmed that the optical ac- 

 tivity of the molecule is not so much due to the chemical contrast 

 between the substitutes round the central atom, as to the degree 

 of symmetry, or dissymmetry, of their arrangement in space. 



From this it appears necessary in all problems in the domain 

 of stereochemistry, always to find out what is the influence of the 

 one, and what of the other of the two factors considered above? 



We must investigate whether in the case of Pasteur's law, the 

 observed properties of the molecule are principally governed by 

 the non-superposable arrangement of the constituent radicals, or 

 by their chemical contrast, or by both causes. Only when we shall 

 have succeeded in separating both these factors out of the fullness 

 of their common manifestations, we can hope to get a clearer insight 

 into the true significance of Pasteur's law, and of the part played 

 by Van 't Hoff-Le Bel's suggestive theory in explaining it *). 



17. With respect to the fact that the occurrence of optical 

 antipodes can also take place, only if the arrangement of the atoms 

 be different from its mirror-image, independently of the special 

 circumstance that certain chemical differences of the substitutes 

 are present or not, we can now at once infer that every chemical 

 molecule must be considered to be resolvable into enantiomorphously 



1) F. M. Jaeger, Proceed. Kon. Akad. v. Wet. Amsterdam. 17. 1217. (1915); 

 18. 49. (1915); Chemisch Weekblad, 14. p. 706732- (1917). 



