292 ORGANIC CHEMISTRY 



regard to the other three atoms or groups as was held by the group 

 which was displaced. The manner in which it has been possible to 

 work out, consistently, the complex relations between a considerable 

 number of sugars, gives a very strong experimental basis for this 

 statement. On the other hand, it is well known that such reactions 

 often give racemic mixtures, which indicates that a shifting of groups 

 with regard to a central carbon atom takes place much more easily 

 than the shifting of a group from one carbon atom to another, at 

 least in saturated compounds. There are also a number of extremely 

 interesting cases where a reaction gives rise to the optical antipode. 

 Thus Walden has shown 1 that 1-chlorsuccinnic acid is converted by 

 silver oxide into 1-malic acid, while potassium hydroxide converts 

 it into the dextro-rotatory acid. It is evident that in one case or the 

 other there has been a shifting of the groups. Again Ascham 2 has 

 shown that when d-camphoric acid is heated with hydrochloric and 

 acetic acids it may be about half converted into 1-isocamphoric acid, 

 and that the latter suffers a similar transformation. This case is 

 more complicated, as a "cis" and "trans" isomerism of cyclic com- 

 pounds is involved as well as the optical difference. Not many cases 

 of this character are known, at present, but such cases certainly 

 deserve further study and must be reckoned with in considering the 

 question we have before us. Le Bel 3 has already pointed out the the- 

 oretical significance of Walden's work. 



While we may feel that we have comparatively sure ground in the 

 application of the theory of van 't Hoff and Le Bel to optically active 

 and to cyclic compounds, the case is quite different when we come 

 to the consideration of what are commonly known as "double" and 

 "triple" unions. Professor Michael has done a very great service to 

 chemistry in showing that the supposition of a more or less definite 

 tetrahedral shape for the carbon atom and of "favored" configura- 

 tions often leads to conclusions which are at variance with the facts. 

 Philips 4 and Blanchard 5 and myself have found a case in which the 

 addition of hydrobromic acid to an unsaturated compound produces 

 an optically active body which evidently has the same configuration 

 as the amino and hydroxy acids from which the unsaturated body is 

 formed by the loss of ammonia or of water. We have here, apparently, 

 a potential asymmetry occasioned by the double union which it is 

 difficult to reconcile with the prevailing conception of such unions. 

 This case is complicated by the presence of a second asymmetric 

 carbon atom in the molecule and is worthy of further study. Rabe and 



1 Ber. d. Chem. Ges. 32, 1855 (1899). 



2 Ibid. 27, 2004. 



a J. Chim. Phys. 2, 344 (1904). 

 4 Am. Chem. J. 24, 428. 

 8 Ibid. 26, 281; 27, 428. 



