2 4 o SCIENCE PROGRESS 



Van't Hoff 1 has predicted that a molecule of the allene 

 type 



xv /x (a) 



>C : C : C< 



y/ \y (d) 



will be optically active, inasmuch as it is asymmetric and 

 enantiomorphous. Substances of this type are very unstable and 

 very difficult of preparation. In 1910 Lapvvorth and Wechsler 2 

 prepared a substance which they thought to be 



C,H 5 s. /C fi H 5 



>C : C : C;' 

 C 10 H 7 / * - COOH 



diphenyl-naphthyl-aller.e-carboxylic acid. 



They tried to resolve it into two optical isomerides by the usual 

 methods, but were unsuccessful. But on account of the great 

 difficulty of handling such substances, their experiments cannot 

 be regarded as decisive. The question is still an open one, and 

 there is room for prediction. 



According to the ideas put forth in the preceding pages, 

 substances of such a configuration should not be optically active, 

 in spite of enantiomorphism, for want of the necessary screw- 

 spiral structure. The deductions drawn from the two hypotheses 

 are at variance with each other in this case, which will therefore 

 serve as an excellent test-case. 



It is usually argued that a structure like this 



XHC/^'V^SCHX 



\(CH,)/ X (CH 2 )/ 



simulates the allene structure, for all practical purposes, so far 

 as optical activity is concerned. The writer ventures to doubt 

 this. He submits that there is a world of difference between 

 the two. In the allene type the presence of the double bonds 

 makes a screw-spiral structure impossible; but such is not the 

 case in the other type, where the spatial distribution of the 

 linkages is similar to that in the case of an ordinary carbon, thus 

 making a screw-spiral structure possible. 



1 La Chimie dans Pespace (1875). 

 ' Trans. Chem. Soc, 19 10, 38. 



