Structural Differentiation in Asymmetric Reactions 165 



would be the same as that of the a groups in the optical antipode 

 ( !aa I — b) ( — b).] Previous discussions have not dealt with dyssym- 



e C— 



I 

 I 

 I 



I 



I 

 I 

 I 

 I 

 f c— 



XIV a 



> +b +b 





I 

 I 



I 



I 

 I 

 I 



d 

 XIV b 



metric structures. Rule 1 in particular is limited to symmetric com- 

 pounds. It may be noted, however, that our finding is consistent with 

 rule 2 since the compound, although non-superposable on its mirror 

 image, possesses a twofold simple axis. As the central carbon is not a 

 meso carbon atom the result is not inconsistent with rule 3. 



Example 6, Caab-Caab {XV) . Internal rotation around the central 

 bond permits two symmetric arrangements (XVa and XVc) . If XVa 

 is rotated 180° around an axis which is perpendicular to the plane 



w 



V/ 



a' b' a 



' T N 



a"" b 



XVc 



\'V 



c' 



b' 

 XVd 



