STEREOISOMERISM AND OPTICAL ACTIVITY 239 



The structure as a whole is devoid of any plane or symmetry, 

 and is not identical with its mirror-image ; but here, as in the 

 case of the inosites, there is no truly asymmetric carbon, although 

 there is a pseudo-asymmetric one, viz. C (1). 



The authors maintain that this is a case where the optical 

 activity is due to the asymmetry of the molecule as a whole ; 

 while Everest 1 and others maintain that C (1) can be regarded 

 as asymmetric, by a suitable modification of the definition. Now 

 this latter view is only a round-about and clumsy way of putting 

 the distinction between open-chain- and ring-compounds, which 

 has been alluded to above. The former view emphasises this 

 distinction more strongly (although in a different form) than the 

 latter, and so far it is better. But what is meant by saying that 

 the activity is due to the asymmetry of the whole molecule? 

 We have seen that this has no meaning, that the optical activity 

 cannot be regarded as being produced by asymmetry, but must 

 be regarded as an effect of a screw-spiral structure of some sort. 

 Such an arrangement, as far as the writer can see, can only be 

 regarded round one particular carbon, and not round the whole 

 ring; and that particular carbon in this case must be C (1). 

 And this is where Everest's view is more suggestive than the 

 other view. 



To recapitulate : we started with the fact that enantio- 

 morphism does not necessarily involve optical activity in 

 crystals ; further it was pointed out, that even if it were the 

 case, enantiomorphism can hardly be considered as the efficient 

 cause of optical activity, but that the nature of the phenomenon 

 suggests something of the nature of a screw-spiral arrangement 

 of particles as its probable cause. And then an attempt was 

 made to apply this idea to the various types of carbon com- 

 pounds, which are optically active in the liquid or dissolved 

 state, and in which, therefore, the activity is due to the arrange- 

 ment of atoms in the molecule. 



So far, the new hypothesis has given us nothing essentially 

 new. It has only satisfied what seems to the writer to be a 

 logical necessity. This logical necessity may not perhaps obtain 

 general admittance for the hypothesis, unless it has been put to 

 a more concrete test. This test is fortunately supplied by the 

 following important case. 



' Chem. News, 1909, 100, 295. 



